You learn a lot of interesting things multi-boxing that single-boxers may never know about.

I remember the first time I jumped with a night elf where on one screen he flipped and the other he didn't. So I immediately realized that the clients just receive the command to jump but each renders it randomly.

It amuses me to know that newbie kids showing off their jumping prowess think that the triple back flip they just pulled off was seen by all. LOL.