Commentary: For what it's worth, here is my vaping progression thus far.
First Device: Halo G6 cigalike kit. Works pretty well, battery life was very good especially for such a small one. Found out I didn't like plain cartos much to use. Cut my smoking in half, easily, without even trying. Found myself looking for that 'something more' though.
Second Device: 900mAh eGo Twist kit. Variable voltage was nice, really brought the flavor out of some juices more at a higher setting as Baditude mentioned. It was still smallish and I really, really liked the way the flavors came through on the clearomizers that came with it. Cut my smoking by at least 80% easily. I did, however, easily break one of my eGo batts while I was at my brother's house for the weekend. Decided to take one more step up so far.
Third Device: VAMO V2. Variable voltage/wattage. 18650 batteries that last me nearly 2 days per charge. Much bigger than the Twist and heavier but that didn't bother me, I actually like the solidity of it. Since I got the VAMO, smoking has been non-existent except for one pack I bought when I was dealing with some stressful stuff....but I also found out that the analogs weren't as satisfying as I was expecting they would have been. Back to VAMO usage and carto tanks happily, though I am going to try the Kanger ProTank and maybe the iClear30 out of curiosity to see how I like those.
So over more than a month now, I've bought a total of 4 packs of cigarettes. Normally during this time I would have probably purchased a carton a week = 50 packs.
Depending on your smoking habit, I'd probably recommend stepping up to one of the more advanced mods if you're looking for that bit more. I liked the eGo Twist and still have my other battery as a backup/occasional use, but I didn't like the fragility of it. I do like the more sturdy mods which are often made out of metal.