Thomas Brand over at Egg Freckles dishes out some harsh truths about the myth of repairing disk permissions:
If you don’t know about permissions don’t worry about permissions. Just keep using your Mac the way it was intended, and Apple will take care of the rest. Leave Repair Disk Permissions for the people who need it.
I find myself mostly in agreement with Thomas’ piece, however, I don’t see any harm in running a disk permissions repair. It certainly won’t cause any issues to your Mac, just don’t expect it to repair much.