Something people don't realize, because I'm not sure how many people use it:
In CS1 and earlier, a layer grouping is not the same as it is in CS2. In CS1 and earlier, pressing Ctrl-G will create a clipping mask, whereas there is no hotkey for clipping mask in CS2.
Just something I noticed that kept tripping me up, as I had gotten used to CS1 hotkeys.
I actually changed clipping mask back to CTRL+G on my copy, the hotkeys are customisable.