I've got both T2 and T3. T2s are working pretty well. Basic top coil with wicks ... swirl occasionally. My T3 BC is having some wicking issues. Not sure if it's the coil base or the
juice. I have a few more T3s on the way to fiddle with. We shall see.
Form factor wise, I still prefer the ViviNova mini I have now. The T2/3 are a little wider than an eGo battery in general, since they have to accommodation the inside threading. I'm finding that in and of itself to be a turn off. T3 is a lot longer than a T2, which is a tad longer than a VN.
Mouthpiece on a T3 is not removable. For the T2 I have seen some vendors carrying replacements. Back to the VN ... uses most any 510 DT.
My brief experience thus far.