I purchased this game last night and only played through the first campaign level, and I was pleasantly surprised at how fun it was. (Sinfulfate messaged me about it a few weeks back and I just got around to trying it out.) The controls are very simple, and the learning curve is only about five minutes or so. It also apparently has 16-person multiplayer modes and a co-op mode which I haven’t gotten around to trying out yet, but will soon.
I know it’s been out for a little while now, but if you haven’t checked it out, download the demo...it's decent and probably the best game I've downloaded in a long time from the marketplace.