In case of doubt see this quote:
With this in mind, smoking should be commenced at as young an age as is reasonably possible. Children who have not yet developed a pincer grasp might require modified cigarette holders, safety lighters or both.
Actually increased hemoglobin levels in smokers wouldn't be surprising. The problem is that all of the increase (and then some, most likely) is bound to carbon monoxide and effectively inert.
However, I think the use of nicotine as a performance enhancer (not smoking though) is a pretty interesting subject. I've tried chewing nicotine gum and using a patch just to see if I noticed a difference (just a brief experiment I would never do it chronically). I did. Much better concentration, focus, energy etc.
I'm curious to see how the "electric cigarette" phenomenon goes. That would be a way to deliver nicotine without the other risks of smoking.
From what I understand nicotine is a carcinogen on its on, but I don't know how strong of one it is.
It would also be fun to see if we could synthesize non-carcinogenic molecules based on the nicotine molecule with all the positive performance enhancing effects.