It was the challenge that was the main appeal for me. Not just within the game itself, but hooking up 5 PC's, networking them, getting Synergy set up, etc. Also there's a certain amount of pride in seeing your group function after writing a bunch of macros for them...

The other thing I really enjoy is that it lets you play the game on your terms. You want to run that instance or complete that group quest? You can do it whenever you like...and no more wiping becuase some nub can't tank or a lock keeps pulling aggro. You really learn to appreciate that tactics of a boss encounter if you're doing it yourself.

In short, mutliboxing breathed new life into a game that was getting a little stale for me.

Cheers,
Stealthy