I am downloading while typing, so I can't speak to the quality yet. These fan games with popular characters always get taken down very quickly, so I am posting about this now while you can still get the game, though Kotaku just ran a story on this game and how it has been 6 years in the making, so the servers are a little hammered right now. Get it before it's gone.
OK, so I have played the first level now, and feel I can say a little bit more about Mega Man: Revenge of the Fallen.
Positives: +Play control feels like classic Mega Man! +Graphics are great in that 8-bit Mega Man style. +Fun large boss battle on the first stage! Hopefully more to come.
Negatives -Complicated password saves. -Full screen mode has black bars on the sides, -Music is ok, but not classic Mega Man levels of greatness. I know that's a lot to ask for, but they are trying to be the real deal and this is where it most falls short in my mind.
Rock Paper Shotgun described it as combining "run-and-gun action with the rhythm mechanics of Guitar Hero, the puzzles of VVVVVV and even bits from King of Fighters." That was enough to get my interest, and upon playing the game it turns out it is even stranger than that. The platforming difficulty is pretty demanding, but so far, doable. What gets crazy is when you start combining that with the rhythm game input presses being thrown at your character. Also, the visuals range from 'children's show' to 'acid trip.'