The first big pile of refuse. Is it possible to play this game properly with keyboard? The jump seems impossible! Am I pressing the wrong buttons? I jump against the wall and then jump towards the right, but always land on the pile of refuse. 
 
EDIT: I have just discovered the run button. Can't believe I made it past the forest world without using the run button. This makes things easier.

Are you holding the run key?

I just bought the PC version, too. I tried using mouse/keyboard controls, and was having a REALLY hard time. I then switched to my 360 controller and the difference was like night and day. I would advise trying the controller out if you can.

LOL, yeah it was the the run key... I didn't even know there was one. It makes the game so much easier. I must have died like 1000 times on that first boss, lil slammer. And yes, the keyboard controls suck.