This game handles multiple playable characters better than any other Classic Megaman game in my opinion. The difference between Rock and Roll is big enough to where you feel like the choice is important and you'll have a preference but not so big that you'll go into some levels thinking you made the wrong choice or having one character be substantially easier/harder than the other. Outside of the character split I found the levels and boss designs to be not amazing or anything, but perfectly fine. It's a Megaman game so it's inherently fun regardless.
Definitely a good fangame, prefer it over quite a few official titles.