Some anecdotal evidence for ya:
I quite smoking January 2, 2005. In the past 8.5 months, I have gained more strength than I ever have before.
Now, I suspect that most of my
strength gains come from also lifting with greater consistency than I ever did when I smoked -- it's hard to say whether the actual effects of the cigarettes were screwing me up, or how much the effects were secondary. But suffice it to say that it's hard to get psyched up for a workout of
heavy squats when you know that you're going to be ridiculously dizzy and heaving for air halfway through your warmup sets.