I'd say that it's comparable to any of the other 3.7v devices that takes a 14500... I've only been vaping for like three weeks and this is my third device. I'm averaging about seven to eight hours on a single charge vaping pretty much nonstop but I'm expecting that to go down as the batteries get worn in. There is a noticeable drop off in performance right before the battery dies and that's usually when I swap it out.
It's not a very big device; not much thicker than the 14500 that it houses; it's got a solid build quality and everything fits and screws in properly and easily. The LED light is mostly understated but given that it actually has a light (as opposed to most other mods on the market) it's not a huge deal. Also, if you place the battery in the opposite orientation, it disables the LED completely to allow for stealth vaping. Button has a nice feel to it and it's not very likely that it'll go off in a pocket or a purse.
Overall, I'm impressed with my Vypr 510 and I'll be sticking with it for a while.