I used to smoke quite a lot (I was able to smoke at work in those days, so it was easy to get through a packet a day) but when I gave up I really didn't notice much difference when it comes to playing the sax. My sense of smell did improve a lot, though, as did my bank balance.
I also used to smoke a lot of dope in my 20s (I know, I know), including while playing. That really did make me feel dizzy. I guess I thought I was being some sort of chilled out dude. In fact, I think it just made my playing crap. The same with drinking while playing. Well, not actually while playing, you know what I mean. Although I'm not the greatest player in the world, I'm much, much better when stone cold sober.
I'd definitely recommend giving up, though. Disposable income, smelliness and health all benefit.