I had some original E2's and wasn't very impressed with them. Too much of the tasting of the wick material or something.
I tried to buy some of the ceramic E2's from Ken but even though the site said they were available, they had vanished.

I've been most anxious to try them so ordered a few "kits" instead from Ken. He kindly shipped them in like 2 minutes.

Regrettably they're prefilled with the Chinese version of Marlboro, which tastes like old shoe. The one I opened had leaked inside its plastic mini-baggie. Excellent -- less gack juice to be rid of.
I find refilling to be a bit vexing because if there's the slightest bit of moisture it's really hard to see the little holes where the needle tip goes in.
However, if I dab a bit of paper towel down there I can locate them again and fill'erup.
I haven't had any trouble re-situating the little silicone ring.
I haven't had any leakage at all. I'm vaping on one fill close to half a day before considering a refill. I'm with Bad; only like a few flavors of carts and mostly would use em, then drip on them till they began tasting ack. Then toss and start over. I did feel like I was dripping most of the day.
I do feel like these things, or some incarnation of them, is the future of vaping. Can't wait to get my hands on some XL ones. Thanks for this informative thread and the other E2 whopper thread.