I'll jump right in so as not to slap you with one of my typical 'wall of text' posts.
EverQuest II has the feature, I love it, and can't see any reason why people wouldn't want it.
The ability to lock your XP to prevent levelling, not only a twinks best friend, but pretty coolio if you like to stick around and suck all the goodness out of a campaign (with a character suited for the level range) before you're ready to move on :).
