This has actually been a large concern for me recently, and make sure you don't ignore it. On my cab it slopes down a couple of inches across it's 14 inch depth. I started getting major pain in my wrist after less than half an hour of playing. I'm about 6' and the angle my hand was at was killing me. I ended up taking the top off, then propping the front up so that it sloped away from me, towards the monitor. That made the pain go away, but obviously wasn't a permanent option.
This weekend I picked up a couple of 29" barstools at Target and put the cp back in it's original position. This totally fixed the problem and I am much more confortable now. So judge based on your height and if you will be using stools or not. Also try to mimick the angle and lift your fingers up to find a comfortable slope. Good luck, and stools still may be on sale at target!