I was thinking about this the other day. When I dual boot installed Windows 7 the other day there were a million and a half things I needed to "adjust" just to make Windows usable at all! When I setup OS X it takes like 10 minutes, tops. Not including app install time of course, but that's a given.
I would say I setup iStat and do a quick run through of System Preferences. Then I setup all of the user folders on a separate 'Data' partition. A few preference changes in certain apps and that's about it.
I love OS X's simplicity.