If you like co-op and Diablo-esque action RPG's, this is an enjoyable, albeit not amazing, game.
The whole system is really rather simple. It's more like Diablo, but even simpler than that. It's simplicity is it's biggest fault really. It just doesn't stand out in the long run as a very deep game. But, for what it is, it is tons of fun.
I particularly like the co-op play. It's great just burning up some hours with a friend smashing the hell out of stuff. It turned into a great bored fall back game for my friends and I. We have a few minutes to kill, so we kill go smashing stuff.
I'm sure there are better ways to kill your time in other more engrossing multi-player experiences. But most of those are more competitive. If you like co-op, this is an enjoyable, albeit not amazing, game.