WOW, what a fun game. Played the demo the other day because I was bored. Ended up wanting to play it again the next day. Turned out, the demo was not enough so I bought it.
While I was playing the newly bought game, I told two friends in my party about it. 10 minutes later we were all playing our newly bought XBLA game online in coop and we played the entire 55 levels in one sitting.
We had a blast and are now going to play it again on hardcore mode. I doubt we will get through it as quickly which is fine as long as we continue to have fun.