I started playing it two nights ago. It plays as a standard third person shooter, except you've got 3 AI squad mates who are actually very useful and clever.
The thing about it though is that it feels highly strategic. It's a bit deeper than a mindless shooter, you're encouraged to take your time an make calculated decisions, and you've got a variety of quite sophisticated tools and weapons to do so.
Don't get me wrong, it has mindless shooting sections in there as well, but really this game caught me by surprise. It's got to be one of 2012's most overlooked titles.
Check out my investigation into 7th generation exclusives here: http://rustygamer.wordpress.com/