HAHAHA. From what I understand after talking to my "Satanic Mechanic," it's an excellent method of conserving time and momentum, particularly if you're racing. HOWEVER, you MUST MUST MUST use the clutch when downshifting, or you'll really mangle your tranny.
It's really just a trick of matching up the rev's with where the bike wants to shift. My old SV650 wanted to shift around 6,500, and anywhere above there she'd hop into the next gear with no problem. It's really the only way to do it if you're dragging with someone (not that I'd EVER do such a thing, because that would be illegal).
--Jaeger
