I tried Zyban when I first tried to quit. Stopped taking it a week in though
Was quite intense, I don't know if it was withdrawal symptoms but I suspect the Zyban.. I was completely on edge and moody. I'd snap at anything (I'm not usually like that)
One thing for sure is, it definitely helped me cut down for a while. Got to a point where I couldn't even finish a cigarette as it tasted so foul!