I must say those are such funny edits of the original sprites.
Anyways, this hack is not brilliant. The design is very lacky, linear, without too much stuff going on. Some other times, instead, felt a bit confusing, especially when you have to use a P-Switch in certain parts in order to keep going. The chances of messing a level up is very high, and sometimes you need to die and restart, since some levels don't have a reset door/pipe. A weird design overall.
The aesthetics, well... they're more or less good. Some were well-made, like the chucks reskin, others were actually hilarious, like the bullet bill reskin, some others were weird, like the... stuff that you see in Mario's house. There are some weird palettes here and there, but it's not too ugly. I liked the overworld.
Overall, a decent hack. The design is a bit weird, but it's still acceptable.