Spent about an hour with the sequel, which I heard of first, and thought was pretty fun if exceedingly frustrating at first. The game delivers on its promise and premise. You are not just playing as the Robot Masters in the game, you are using their original mechanics in all their glory and with the strengths and limitations that brings. Air Man can not move or jump while using his weapon, but he can force winds that alter some of your enemies' movement depending on the direction you face. Metal Man fires in all eight directions and can set up interesting trick shots with diagonal firing, if you have the patience and foresight. Crash Man...is the bomb, I will say nothing more about him since I'm biased.
Be prepared, though, because the learning curve is not just difficult, it's frustratingly so if you're ingrained with the original control and mechanics of Mega Man himself and you'll experience a period of teaching yourself a new way to think with every character. All in all though, as a freeware game it's very fun and worth a look, despite the urge to bust the keyboard with your fist.