I used the old cartomizers sold here (white box) for a decent time and had good success with them, other than finding a long period of time when the battery was low where I would get almost no vapor at all from the carts. But, they didn't gum up quickly and lasted quite a while, so I accepted it.
Now, with these black box carts, I find that I can't tell when the battery is about to die until it does - I get smooth, heavy vapor the whole time through. However, these things spit like crazy if you even get close to overfilling them one time, leaking out of the bottom, where the threading is, and much more annoyingly, spitting small amounts of eliquid into your mouth with each draw until the fluid level gets down to a more functional level. You can actually hear the cartomizer gurgling if it's overfilled.
These guys also die a bit faster, gumming up quickly. I'm going through them much more rapidly than with my old cartomizers. I really would like a choice between the two, because I would go back to the old brand if I could. However, as far as available refillable cartomizers go, these are still the best out there that I can find right now, so I'm sticking with them. Good luck and happy vaping!
7th Jan 2013