I just switched from Photoshop CS3 to CS5 and holy cow there's a serious learning curve! I don't remember having this much trouble with Photoshop since maybe CS1. I think the thing that's bothering me the most is I can't right-click on the top of the photo anymore to resize and change the canvas size. I used that trick on every photo for years and years. Actually having to go to the Image menu or use the key command seriously slows me down. Took me a while to figure out how to tile my photos, too. I hate having images stacked in the workspace so I can't see them.
This is a change that had to be made but I sure hope I can get used to it quickly.