I also used (still do) Chantix. The first time I tried it, I stopped taking it after a month and I relapsed back to smoking. Second time, I quit (July 20) and have stayed on Chantix and have NOT SMOKED! Yeah!
Here is what the drug does for me: 1) it relaxes me and takes the edginess away (not surprising as it is a derivative of the anti-depressant Welbutrin. 2) makes cigarettes taste horrible (which helps me) 3) I am sleeping well, but having lots of dreams 3) it reduces my desire for alcohol (used to love wine, but have slowed down alot) When I do drink, I have strange dreams and sleep poorly.
I have not stopped so I can't comment on withdrawal problems. I do plan to continue Chantix until I feel completely in the clear. I think that will be several months. I have previously taken Welbutrin and had no bad effects, so I expect the same for Chantix.
Overall, Chantix has been very good. I had tried hypnosis and gum and patches, but this is the first time I have felt like I am finally breaking free from cigarettes! And I have smoked my whole adult life!
So, good luck. Did you ask your doctor about slowly reducing your Chantix dosage? This is usually the best way to get off of anti-depressant meds.