If you can play with another player, either on your system, or over XBL, then I would have a hard time finding a better co-op game to suggest to you. If you are up for a mind-stretching challenge, Uberschizoid mode is certainly worth it, as well. If, however, you wind up playing alone, you will find that the computer doesn't make for a very good partner after the first 35 levels, or so.
This is a blast to play with a friend, though. Though the gameplay doesn't vary too much, this game gets extremely challenging, and I found the "I got your back" aspect of the co-op fantastic.
