depending on who you talk to, we could be on rev. a and we could be on rev f or whatever.
They've made tons of small revisions to the MBP, it's not the same machine as it was when it was first released.
However, nothing major has really changed to differentiate one rev. from the next. The next MBPs supposedly will have Merom and a case redesign, so you'll definately know it when we hit rev. b, in my opinion.