I have been using an ego-t since January without any really noteworthy problems. It works for what I use it for, but it has never been my only PV. --- The eGo-t produces cool vapor and mutes many flavors. I still like it for mint juices and some other really sweet or strong flavors. I never experienced any serious leaking problems or dry hit problems that other people did.
OK - that said: The 510-t is a completely different animal. It produces warm, flavorful vapor. It's very close to dripping without the occasional dry hit when you forget to add a couple of drops. I used the 510-t for about 10 days and I liked it quite a bit. I had no leaks, no flavor problems, and no dry hits except when the tank ran dry and I didn't notice. The capacity of each tank is only about half a ml, so it just wasn't an appropriate system for me. I vape anywhere from 6 to 10 ml a day, so swapping tanks so often was not what I wanted to do. I traded it for something else, but not because there was anything wrong with it... just the capacity of the tanks.