I'm not a huge fan of the cartomizers, although they do work. That said, while I've had some minor leakage issues if I'm on the fourth or fifth refill of a tank cartridge (I use eGo-T "A" tanks), replacing the little silicone stopper tends to repair that. Unlike some of the other people here, I haven't been experiencing major flavor issues, but at the same time, I've been sticking with a couple core flavors. The biggest problem I have with the tank system is that thicker juices and darker colored juices (like, for instance, the coffee juice I was playing with the other day -- which is very thick and is dark brown in color) tend to gunk up the wick, which gives a burned taste to other juices. There are YouTube videos on how to clean your tank attys, and I highly advise watching a few of those. I'm likely to pick up a eGo-C atty in the future to experiment with, too... I hear those are even easier to replace (although I did find a place where the eGo-T attys weren't too terribly expensive).
For me, I guess I just like it being just the juice, with no filler. Everyone's got a different view of it, though. Test a few options - cartomizers, atomizer/cartridge, tanks - and find out what's best for you. The great thing about the eGo-type systems is that they tend to be 510-threaded, so a lot of options are available.