Obviously, a game in which the characters play Space Marines is going to be fairly combat heavy. But how much opportunity for social interaction and real role-playing is there going to be? It's established storyline that some liberal chapters give their Marines up to 15 minutes a day of free time - everything else is scheduled out for them.
The description says "there are exceptional roleplaying opportunities" due to characters being from different chapters, but this doesn't seem like a huge obstacle to me: You'll work together because those are your orders, and you're Space Marines, and if you don't follow orders you are a heretic. The end.
Is there something I'm not thinking of?