As mentioned previously, I have for a while been considering running some Traveller, in a very desultory way, and started playing with the world-creation tools.
There are a number of potential "issues" with Traveller world creation. While I've spotted some of these myself, they're backed up to some extent by comments from others around the Net. As so often, this is an impressions-in-progress sort of post, and whether apparent "issues" actually end up being a problem is yet to be seen. Things that seem weird from one point of view may work perfectly well in play, and things that seem arbitrary may let you build a perfectly reasonable universe.
One of the issues is that the world-generation rules are inclined to produce one type of world: small planets with poor atmosphere and tiny populations. Note that these are "the single most important world in each system", and thus all other possible planets, planetoids and general astral bodies nearby are less significant.
Size is rolled as 2d6-2, which tends towards 5. For reference, Earth is a 7. Only around a quarter of worlds will be Earth-sized, let alone bigger. However, Traveller seems to treat "world" as being "habitable unit", and so things like moons around a gas giant are a "world", whereas the planet itself isn't.
Atmosphere is 2d6-7+Size, which tends towards 0+Size, and so towards 5. This gives a thin atmosphere. Here, we're dealing with 4d6-9. Fully one-sixth of worlds have so little atmosphere that a vacuum suit is required at all times. Four in ten have toxic atmospheres. Allowing for the rare Unusual worlds, plus those with only a few habitable regions, this means only half of habitable worlds are actually, y'know, habitable.
Hydrographics is 2d-7+Size modified by atmosphere. This tends to create worlds with a reasonable amount of water (7), except that those with very low or high atmosphere, or high temperature, reduce this significantly or eliminate it altogether, leaving the average at "not that much water". Again, fully one-sixth of these habitable worlds have neither atmosphere nor water. They must have pretty good technology to remain alive for any length of time in that situation.
Population is 2d6-2, tending again to 5. This gives an average habitable world the population of the average modern city, with which they nevertheless maintain functioning societies, education systems and (sometimes) high technology. You might wonder why they don't just move en masse to one of the nicer worlds with atmosphere, water and tiny populations.
I would also note the following important quote:
Planets with a Population of 6 or less are very small colonies, and may differ considerably from the descriptions in the rest of this chapter.
That is, more than half the worlds generated - about 58% - are likely to deviate from the descriptions given. This makes me wonder why they didn't instead come up with descriptions that do suit the majority of the worlds and have an "exceptions" sidebar for the handful of planets that have a population greater than the Isle of Wight.
TL is an interesting point. TL needs to be 8 to equal modern developed-world technology, and 9 or 10 for feasible interstellar travel. TL is 1d6 with a bunch of modifiers for all the things I already rolled. In the vast majority of cases, modifiers will be a +1 or +2, leaving you with an average TL of 6ish. This corresponds to about 1970s technology - notably, they don't even necessarily have an internet.
From what I can see, only a bare handful of planets are likely to achieve TL 9 and be in a position to really support a spacefaring setting. In theory this doesn't matter because the spaceports handle ship maintenance, but it leaves a bit of a question mark over how all this is supposed to work. What if something goes wrong with the spaceport..? Perhaps more importantly, it leaves you with a sci-fi setting in which you use hypertechnology to jump from world to world, negotiate for jobs with cyberaugmented alien contacts in bustling spaceports, and then walk around somewhere that looks like this. Is this what I want?
From what I've read elsewhere, there's a perceived problem that Traveller can readily roll up one-off worlds, but doesn't really offer much support for producing a coherent set of worlds that make sense in a star-travelling context. You need some high-tech worlds, for example. You need trade hubs, and centres of political power - planets that have either economic clout or cultural clout (preferably both), plus enough technology to feasible influence nearby worlds. If you want any kind of stellar empires going on, then somewhere needs to provide high-tech, high-population worlds with the kind of culture that might conceivable engage in stellar imperialism - simply having a high-tech world isn't enough if it's barely-populated and has an utterly insular culture. So that kind of thing you really need to generate yourself. The random worlds only really work as planet-of-the-week for adventuring.
I think the main thing that can seem strange, though, is that technology can vary wildly from one world to the next, as though there is basically no transfer between them. Now obviously this is more difficult than in a planetary setting, and there are many cases where small, poor worlds might well be unable to sustain high technology, but it seems to me that as a general rule, non-despotic high-tech worlds should spread some technological progress to nearby worlds. If they're alien then some kind of Prime Directive might be in force (in which case, they should be Red Zoned) but if they're human and open to trade, how come they haven't picked up such useful things as telecommunications, medicine and clean renewable energy? It's particularly noticeable on large, well-populated worlds that should be able to sustain a knowledge base. Once I've finished building a sector and determining trade routes, I'll have a better idea of whether things end up being unintuitive.
You also don't get any information on subsidiary worlds of the system, even though (say) mining or scientific testing on nearby planets is far more probable than doing so in another star system entirely. Such worlds are described as "less habitable" than the primary worlds, which makes little sense to me given the kind of primary worlds Traveller seems to generate. If that is the intention, I would be strongly inclined to tweak the system so that primary worlds are largely, y'know, habitable and the less-habitable worlds fit the patterns of the default rules.
Just in passing, I wonder if Balkanisation is a little underweighted. It seems to me that, given human tendencies and the potential for aliens, a rather higher proportion of worlds should not be under unified governance? But I confess I am not especially clear on how factions are really expected to work, so this may be related. If strong-factioned worlds represent disparate governments with a veneer of unification for interstellar tarde, and Balkanisation represents worlds without such a veneer, that may be the answer.
I also notice that the chain of population -> government -> law tends to lead to places with Law ratings of 0-3 in most instances. This may in fact be exactly what they intended to do, as it leaves PCs able to get on with things largely unmolested by the government. However, I have to say that I personally find it hard to swallow the number of planets that are happy for people to wander around with assault weapons or better. Even today, these are unacceptable in the majority of places, and the higher the (roughly) technology level of the region, the less acceptable they tend to be - America being an aberration in these matters. I don't think it's necessarily a problem from a gaming standpoint, although it might incline things towards force as a default task resolution system, but it does seem a bit implausible.
I think the main yerwhat? factor is the presentation of the ban table, such that the weapons and liberties scales look wildly out of synch from the British point of view: banning most weapons apart from shotguns (and why those are a separate category I can't tell you) initially seems to be equivalent to discouraging visits and limiting offworld news, while the full-blown weapon ban common to most European countries appears to be treated as the equivalent of North Korea - no visitors, no emigration, no free speech, no unfiltered information, not even C20th technology items. When you actually look into it, though, the contrast isn't likely to be a problem, because of the way government type interacts with bans. They aren't really presenting different categories of ban as being equivalent, the table is just a handy way to arrange informaiton in ranks.
The most awkward bit for me, though, is the number of worlds that achieve a Law level of 0, where there are basically no restrictions on anything. Apart from the sheer unlikeliness of it (I'm pretty sure that even tribal societies today, which is what low Government approximates, would want to stop people from wandering around with WMD or life-devouring narcotics, and control of territory is even more widespread) it doesn't really make sense with many types of government. A corporation that doesn't control its employees and where you can get off a murder charge for a handful of credits? A feudal government that doesn't impose feudal-style rules? I am sceptical.
A question of dice
Finally, a question: a lot of world attributes are based on X - Y + Z, which can be interpreted in two ways giving different results. For example, Hydrographics is 2d6-7 + Size. If this is like maths, then the average will be 5, as Size is usually 5. However, it's possible that they intend you to apply a floor of 0 before adding attributes, so a roll of 3 gives you 0 + 5 = 5, rather than -4 +5 = 1. In this case, almost all values in the system would end up higher. This is particularly significant because you're often combining multiple penalised rolls. To get a high Government, if you roll 2d6-7 + (2d6-2), allowing negative values on the first part: having done some painstaking maths with several big Excel tables, this leaves 9% of worlds with any of four autocratic governments, while 6% are run by corporations, fully 10% have no government worth speaking of, and 11% are run by outside influences.
However, let's say you're rolling (2d6-7 >=0) + (2d6-2), treating them as two discrete zero-minimum elements that are combined. This gives you 10% autocratic governments, while 4% are run by corporations, only 2% have no government worth speaking of, and 14% are run by outside influences.
It's not a massive difference for the most part, but the proportion of government-free worlds is much lower with floors for both parts, and this has a significant effect because of its knock-on effect on Law. Law = 2d6-7 + (Government = 2d6-7 + (Population = 2d6-2)). Worlds that might have a Law level of 5 with floors, end up with no law at all without them. Getting specific, rolling all of the relevant stats without applying floors, as 2d6 + (2d6 + (2d6-2) -7) -7, leaves you with fully 13% of worlds having Law 0, half that regulating only the most dangerous activities at Law 1. In contrast, if we treat each 2d6-7 roll as separate from the attribute it derives from with [(2d6-7) + ((2d6-2) + (2d6-7))], then only 1% of our major habitable worlds have no functioning legal system, and they tend to cluster around the 6-10 mark in quite repressive governments.
So I'm just curious what the general practice is. I've modelled it without floors so far as there was no indication otherwise.