Me and my girl stopped 2 years ago.
The first weeks were very hard (I smoked 40 cigs per day, she did, too).
I couldn't sleep and I was tetchy. We gain weight. We needed the help of a doctor. I NEVER imagined that quit smoking is THAT hard. I felt like a drugaddict (well in fact I was). After 2 months we liked it very much (everything smells better, tastes better, etc.), but our problem was: All our friends still smoked.
So after 14 months, new years eve, we were at a metal-concert (Pain, Theatre of Tragedy, etc.) and we were drunk. So I said to her:"Mh, I'd like to smoke only for tonight!" And she said:"Well, I thought the same." So we bought just one pack. (Everytime I drank alcohol I wanted to smoke)
Next week we smoked 4 cigarettes per day and some weeks later we smoked 40 like we did before our 14 months break.
Today we're still heavy smokers and we know one day we'll try again.
My father stopped after 30 years: He had NO problems at all. He's happy.
My uncle started again after 9 years without it (!!!!). He woke up at night and had the desire for a cigarette. He bought some and started again.
So if you stop, don't make the same mistake like we did:
It's like alcohol: You're an ex-smoker for your whole life. NEVER think:"Well, I'm not addicted anymore, so I can try just one cigarette. I'll have no problem with that." THAT's dangerous, because your brain never forgets the addiction.
So good luck. It's worth the trouble!