Not really my cup of tea...
Yeah, I see what you were trying to do here, it's supposed to be balls-hard, like many other platformers before it. Truthfully, though, the only part I found really difficult to negotiate, or at least, the hardest part, was the slipperiness of the controls. Lastman slides all over the place, I died like 3 times on the very first bouncy platform in 1-1 because I'd fly right over it rather than just dropping down. I feel like it's a little bit of a cheap shot for one of the factors that make this difficult is the controls rather than the actual obstacles in the game.
I have to admit that I haven't finished any of the levels, but I've at least tried them all a number of times (is that guy who appears on the level select and says "You're getting better!" supposed to be mocking or sincere?), and besides being difficult to actually execute, it's sometimes hard to figure out what exactly to do, level 1-3 has me alternating between standing on the little arrow block to go into the sky and falling down pits on purpose (sometimes you don't die right away and you can walk a bit. glitch?).
I'm always kind of wary of these sorts of games, because I don't really see the point. Yeah, it's hard, but so what? Play anything enough times and you'll eventually win, so I'm left thinking that the creator has some kind of superiority complex that only him/her and a handful of really tenacious gamers can (or for that matter, want to) play it through to completion.
Anyway, play this if it's your thing, but otherwise, you'll just end up getting frustrated and leaving an angry review about how the platform with the arrows pointing to the left at the beginning of level 1-1 keeps disappearing whenever you go right. (hint, hint)