Mine has white knobs with no little direction arrows; I bought it shortly after the initial release of the OCD so I'm pretty sure it's a V1. How is a V1 different from the current version (V4? Really?)? I like my OCD a lot—it's got a bit of barbed wire and broken glass to it that my other, smoother pedals lack. Do the newer versions retain that edge?

The Fulltone site has a guide to the versions that goes by serial #. I think that subsequent versions of the OCD have tended to tighten the bottom, increase the mids, and make the treble less ice-picky.
fwiw, I preferred v.3 to v.1 for the above reasons.

Hey Flea, there is a comparison between a V2 and a V4 OCD on youtube:

http://www.youtube.com/watch?v=JI5_kdqhBX8

There are very slight audible differences between both but the only way to fully hear any eventual differences is live, videos don't translate the nuances of tone very well.

Thanks you guys. Very helpful. You know you've got yourself some serious GAS when you're thinking you should own two versions of the same damn pedal.

Hey Fleabiscuit and crew-- check this out:

http://www.pedalarea.com/ocd.htm

Article explains the versions and stuff,,I have an OCD on my "next purchase list" and I am also looking for a boost to compliment it...I have a Carl Martin Hot Drive n Boost the drive side is so so (thin) but the boost side is huge, makes my amp sounds twice as big!!! The boost side takes the blanket off the amp big time...If I could find a stand alone boost that was similar....

Monty, very cool website, man, thanks!