I'll just point a few down-sides:
1. The overworld is not changed.
2. The underground part of the 2nd level has a monty mole that when he jumps he goes up into the ceiling then dances in there for no reason.
3. I saw a bit of cut-off-ness in a few parts of the P-switch bridges.
4. The castle's first part is a remake of a Mario 1 level. Please change.
5. The room before the boss looks like it hasn't been edited that much.
6. Ubber Plains is a remake of Level 1-1/Level 1-2. Change.
7. The level 1-2 part had Piranha Plants that had stems hidden in the pipes.
8. The Cave level after Ubber Plains had "OMG!" in a text box, don't put OMG or LOL or ROFLMAO in your taxt boxes.