Brutally hard, sometimes unfair, but strangely rewarding.
Let me get this out of the way first: Megaman Unlimited is a fantastic game. The fact that it is a fan game makes it all the sweeter. The boss designs and concepts as well as their stages and gimmicks are excellent and seem well thought out. Each new stage brings something new to the table and forces the player to account for new concepts to adapt to. The Wily stages bring all concepts together in a mish mash of brutal awesomeness that the player must constantly react to or fail...many, many times.
Which brings me to some of the negatives, this game is punishing. The majority of the stages (great note was taken on the Wily stages, they are painful) are rather long and the midpoints are not placed well. Sometimes the midpoint is placed too soon, leaving 3/4 of the level left to go. Other times its placed too late making the later half a cinch if you die there, you don't have to go back too far. And a fatal flaw was Wily stage 1, where if you died at the boss, you are sent far back to a midpoint requiring Rush Jet to get back to the boss room, if you had used up all his energy and picked up all energy pellets along the way, you were completely hosed in getting back to the boss and basically have to lose all your lives to restart..the..entire..level.
Despite these glaring flaws, the game seems well polished and there are very few bugs or glitches with the game. Mega Man feels a bit 'heavier' than usual but he controls as he should and after getting used to his new 'weight,' making all those jumps and leaps begin to come naturally as you play. There is even rumors of an updated file that will have bug fixes and some gameplay difficulty dummying, which should appease fans who were expecting a slightly less brutal experience.
All said and done, if you have the patience to keep trying and trying and trying a level until you get it right, this is definitely the Megaman fan game for you!