So I was using an Omega at 6v but wanted to try something that would allow me to go to a smaller unit like the Alpha or BB. I got mine Saturday and I can't be happier with how they perform. I'm using an 18650 battery and the draw, flavor, and vapor production is just about perfect. I've been using the same carto for two days now and it's still going strong, but I can't comment on the Constancy between multiple cartos yet. If I can get 5-6 days out of one I'll be sold for sure, and get myself a smaller device.
The only down side if you want to call it that, is I'm use to just topping off my cartos when they start to get low by dripping. These you'll want to actually fill from the bottom to ensure both coils are wet. Takes more time of course, but they last a lot longer than a reg carto does and doesn't need to be filled/topped off as often. Then again I was using my reg Carto's at 6v, so I'm sure That was burning through juice a lot faster too. Either way, if your on the fence with trying these I recommend you do.