Pretty good
I got up to the part just after the spaceship--where it seems everyone is having trouble--and quit. I'd have continued, but Newgrounds was helpful by refreshing the page when I logged in and I lost all my progress.
There was a downhill slope (going left while traveling left) with spikes at the bottom that was particularly egregious with its hitbox; there was a plant just my side of it, that it seemed as if it was also a spike (but clearly curled) as as soon as the character reached it/she/it, he died.
The part I got stuck on particularly frustrated me, as earlier in the game it was particularly notable that we could only make 2 block wide jumps, and this one is FOUR. The ramp obviously gives a little bit of a speed boost, but as the controls were unresponsive while sliding (probably an "in air/falling" flag getting set), the closest I came to making the jump was hitting the landing spot in that pixel perfect spot where I hang in mid-air briefly before falling down (like I hit the corner and the game isn't sure which way I'm supposed to be able to go before gravity asserts itself again).
So yeah.
