I used it 4 years ago. The only problem I had was a bit of sleeplessness. I took it for about a month before quitting the cigarettes. I set a date and for about a week I smoked 1 or 2 a day until I decided that I wouldn't quit until I actually quit. Since that day I haven't smoked one. I continued with the Zyban for about a month to a month-and-a-half after I quit the cigarettes, then went down to 1 in the morning for a couple of weeks and then stopped the Zyban altogether. All the while I was monitoring my blood pressure and didn't even have to adjust my BP medication.
Worked like a charm for me. Your mileage, of course, may vary.