Battery life and voltage regulation. I do agree that, overall, V2 makes a good product. The batteries have done a decent job so far, but it's the cartos that really shine. The price for the batteries ($25) is outrageous, but the cartos are very well priced. Even some of the flavored ones are pretty good. Not as good as some of the made-to-order vendors you can find here on ECF, but not bad either. Menthol is great, coffee is good, cola is good, and my personal favorite is the vanilla. It's more like a vanilla tobacco, not a sweet vanilla cream. Heck, I am even thinking about grabbing one of V2's soft carrying cases...
V2 Soft Case - V2 CIGS
Nope, nothing wrong with V2 if you already own one. Works just fine. However, if you don't have one yet and are looking, there are better options.