Positives:
• The world map retextures were fantastic. I didn't even think it was possible to convert World 7 into a huge airship.
• Many levels had entirely unique themes, used hardly more than once. It takes a lot of dedication to implement an entire tileset just for a single level.
• The ghost house puzzles were very clever and perplexing. You should consider doing a puzzle-themed hack, it's clearly your specialty.
• I know you didn't make them entirely by yourself, but most of the backgrounds were beautiful, 7-1's background especially.
• World 8 was pretty awesome. The level design was a little better than the rest of the game and there weren't a load of cheap "fake difficulty" gimmicks like I usually encounter in late-game Mario hacks.

Negatives:
• World 6 was a huge disappointment. When I saw the star icon, I was pretty excited for a space world or possibly a bonus-style world. When I instead saw it was a second desert world, I wasn't happy about it. You missed a pretty big opportunity there.
• The sound hex is wrong in nearly every castle level. Silent Thwomps are very unprofessional.
• There are way too many blind jumps throughout the game. If you want your levels to include bottomless pits, make sure there isn't too much vertical scrolling.
• The fact that the game rewards you for playing on easy mode (Luigi) is a pretty huge flaw. Not being able to unlock all the star coins while playing as the clones only encourages people to play as Luigi and avoid the clone challenges entirely. It would have made a lot more sense to have those star coins inaccessible to Luigi and available to Clone Mario instead.