Bupronin was released as a smoking-cessation aide under the name Zyban thanks to Wellbutrin's mostly unfounded reputation as seizure-inducing. GlaxoWellcome panicked somewhat after inconclusive studies claimed that Wellbutrin caused more seizures than other antidepressants; as it turns out, the seizures occurred among .4% of patients, most of them already seizure-prone. But the reputation stuck with many physicians, so Glaxo "re-branded" bupronin.
Many HMO's, including BlueCross BlueShield, do cover Zyban and other drugs to combat nicotine addiction. This makes sense financially, since non-smoking customers tend to have lower rates of costly diseases like lung cancer.
Trouble is, some of those companies only cover Zyban for a few months, as there's little point to suppressing nicotine cravings when one hasn't smoked in months. Wellbutrin, on the other hand, is often covered indefinitely, as bouts of depression can last a great while.
Zyban is supposed to take 2 weeks to "kick in"; during that period, you may wish to use some type of nicotine (the patch, the gum, the inhaler, or the new smokable nicotine sticks) to stave off cravings. I've been on Zyban (actually, Wellbutrin -- screw you, HMO) for 2 weeks and have had a very easy time not smoking--in fact, I ditched the patch the other day--but this may be the placebo effect. YMMV. Just take it on a full stomach, because even placebos can upset your tummy.
Oh, and if you plan on using non-medicinal (read: illegal) psychotropic drugs, please read the wu at Wellbutrin, and whatever else you can find, as there exist some bad combinations.