Pretty cool. Didn't get to far with it but I noticed the following:
1) As perspective said the mushroom was replaced by a coin
2) The tunnel before the gap is missing
3) The physics seem wrong: While in the air if you stop pushing the left arrow key you instantly stop moving. IIRC the game kept the arc.
4) The orginal game was a single direction side scroll so if you went past something you couldn't go back to it.