I actually ran through Easy mode myself a couple of days ago. That has got to be one of the most hilarious things I have ever seen in gaming ever; they pretty much hold your hand through the entire game, babying you with random Yashichi on the ground and platforms that cover up 80% of the game's traps. The bosses are toned down quite a bit as well (i.e. Pump Man's shield has only 3 orbs). The game was so easy that I had to do it sans-helmet just to get a little challenge out of it. XD Needless to say, I racked up quite a few achievements on that run through.
Hard mode, on the other hand, is quite grueling, yet fun at the same time. I'm pleasantly surprised that Inti has finally grasped the true meaning of Hard Mode. They didn't nerf the player at all, choosing to solely beef up the enemy layouts, minibosses, and bosses. Shoot, I'm even more impressed at the fact that the Robot Masters get EX moves (Chill Man's is just plain nice!).