Wow... I watched the dev diary just the day before it was released and I didn't imagine it to be so hard. It's the Mega Man effect, just without level checkpoints. You run, you jump, you run again, and then you jump into a projectile that would not have hit you and you think to yourself, "Why the hell did I jump there?" And then you start all over again, because it CAN'T be that hard, can it?
Level 1 no problem, level 2 was hard, level 3 even harder, level 4 seems impossible already. On easy.
It reminds me of the jump'n'runs that I played on my C64, complete with retro chiptune music. I love it! The only thing I miss is the ability to duck or drop through floors while decelerating.