It's great. It and Halo are the best shooters on Xbox still. It has a steep learning curve though, you HAVE to be good with the gnasher if you don't want to be frustrated to hell and back.
Only gun I've bothered using is Gears is the Retro Lancer. I don't understand why anyone would use the regular lancer compared to it. Fire in 2 shot bursts or single fire, it has a very short kill time. I suck at third person shooters, but I mop up with that thing.