On a per user basis it is as safe as can be expected. There have been reports of adverse effects (as with all drugs) and some media reports of sudden deaths, but as the people taking it were high risk heavy smokers with health problems some sudden deaths would be expected!
Ive not got any personal experience with it but the clinical data suggests it can be effective.....I would try all the rest first though...suppport groups, danger point analysis, alllthat.