I'm still young (26), so I think now would be the time for me to quit.
I've sort of fooled myself into not worrying about it too much, because I'm what you'd probably call a "light smoker". I've never had a pack-a-day habit (1/2 at in my peak smoking days), and now I have 2, maybe 3 per day... certain days I go a little crazy with them and have a bunch, but the average is low. Sometimes I go days without one, then will light one up when I'm having a pint or something.
Still though... I feel like am at that point of "why bother?". and everytime I smoke one, I hear that voice in my head that says "i'm not even really enjoying this" (unless it's with beer, for some reason that combo. is outstanding).
I really wish my girlfriend would quit. She has the most beautiful and amazing voice, and the while the smoking hasn't effected it much yet, I know it will eventually. She's a much heavier smoker than I am.
I've quit a few times in the past few years. If any of you are looking for a tip... I find that chewing sun flower seeds is a pretty good "diversion". Helps with the oral fixation thing.
For those of you that did quit, maybe share some things that helped you get through it. Whenever my GF tries, she gets horrible mood swings, gets short-tempered and restless. It can be tough to deal with sometimes.