Im going to pass on this. Bought the previous Alien Breed title on XBL. Singleplayer was so so, rotating the camera is a bit iffy. Multiplayer... hmmm multiplayer would be good... if there was anyone online at the time playing it!
If you've got Unreal Tournament, give Alien Swarm a bash at least its free! And I second what people were saying about Shadowgrounds and Shadowgrounds survivor - they were pretty fun too.