This is an excellent game. I am addicted XD
One pet peeve though: The pipes are set up wrong. In the original Mario Bros., when the enemies would go into a pipe at the bottom, they would go to the pipe directly above them, making it so that they could alternate directions. In this, though, the enemies come out the pipe they started at. I don't know if this is intentional, but it annoyed the heck out of me in the first few levels. Also, I noticed that when you jump fairly close to a ledge, you hit an invisible block. You can also stand on this invisible block sometimes.
That aside, I love this game, though I think it would be even more awesome with unlockable characters for multiplayer mode, like Luigi, etc. XD