Originally posted by Incidents Happen
its true that most sit on their right leg, but as others said, it does not help you reach the end of the neck. thats what the left leg is for.

Depends which end of the neck you're talking about. By "end of the neck", I meant the lower frets. I'd call the heel the start of the neck. But that's just semantics; as you and others have said, if you want to play the higher frets, sitting the guitar on your left leg may help.

Sitting it on your right leg is certainly going to get it nearer the position it'll hang in on a strap. That makes the move to playing standing up a lot easier, in my opinion.