From the perspective of athletics, health and fitness. I would advice against it, it's a personal choice though. I think the best way to decide, would be to give weight to the pros and cons. Then see which way the scales tip.
Although my personal opinion, the negatives seem to outweigh the benefits. The impact it would have on my cardiovascular performance would completely fuck up me and my marathon training. Furthermore, I have asthma, so inhaling something on a regular basis that has detrimental effects on my lungs, is even more ill advised than normal. I also, can foresee it eating considerably into my finances, which I really can't afford right now. Then theres also the inconvenience of the smoking ban.
The benefits, to be honest, whenever i've smoked (socially) in the past, I haven't felt any real significant benefits. Smoking just doesn't do it for me.
The choice is yours to make though. But I think you should seriously consider your health.
I noticed you mentioned weight loss as a benefit, feel free to shoot me a PM if you want any tips on healthy ways to lose weight.