The Siege of Mersadie Hive was a custom scenario lovingly crafted by Arthur. As such, unless your GM is planning to borrow the scenario by hacking together what they hear on this episode and the notes on Arthur's blog, there's really no spoilers to worry about.
As always, be aware that the podcast is not really family-friendly, and features some background noise, if that sort of thing bothers you.
I really enjoyed having the catch-up notes for the Scouts. We had a lot of fun with the boy-hunting aspect in the first game, and while I wouldn't encourage a DM to put in that much effort unless they were enjoying it, the reports really helped tie things together and set the silly scene for our new mission. It also helped with the development of personalities for the Scouts and a bit of relationship between them and the Marines.
Briefing sessions are hard to make fascinating listening, but especially in a mission-based game like this, you need to spend time on them to lay the groundwork. I like this kind of thing, because I enjoy finding out details of the setting and picking up clues for the adventure to come. As you can hear, I get a bit carried away in terms of research - Space Marines have a fairly practical amount of information available, they're not Wikipedia.
This is actually a rearrangement of the material. In the original game, we say "right, let's go" before spending another full half-an-hour on other questions we thought of and yet more shopping. K was not impressed. I reorganised it for your listening convenience.
On that note, I'm never quite sure how much of the planning stages to leave in, and I tend to be pretty lenient with it. I cut out anything that's neither relevant nor particularly entertaining, and also some quite entertaining stuff that's especially disconnected from the subject at hand, i.e. Actual Play. Am I leaving in too much boring shopping? Not being aggressive enough in paring down questions and answers to the essentials? Or is it just about right? Responses from anyone not appearing in the podcast would be particularly welcome...