I played Skate over and over for hours tonight at a friends place. The game is so damn challenging that it makes it addictive. I think my favorite part is that you can actually see yourself getting better. The lack of a grind button seemed weird at first, but the more you get used to it, you figure out where to put your weight and how to lock in to each trick.
Manuals, by far, were the hardest for me, which just made it feel so much more realistic. You actually have to work for your tricks as well. It took me a good five minutes to figure out kickflip backtails, then another few for 270 out, bigspin out, etc.