Wanted more cushion space on the system. I went from 55-60% used space to under 33%.
Piece of cake. The third generation aluminum systems make the disk available just by removing the back or bottom plate of the computer (10 screws).
I used Carbon Copy Cloner to duplicate my disk a day before the operation, then again for an incremental just before the move. Default setting on CCC serves this purpose perfectly. But be sure to switch from the old-style File Vault encryption to the new-style (Lion) encryption before using CCC. That can take half a day by itself.
It was so easy to make the change that I forgot to transfer the torx screws that snug the disk into the bay area. I heard the disk rattling around in the housing when I flipped the system over to turn it on. Still very easy to open everything back up and correct my mistake.
And it is fun to say "Spudger" authoritatively in describing the exercise.