For a month now, I've been using one given for testing. It's part of my daily rotation.
The heating cutoff is quick -- less than 3 seconds -- but the vapor is adequate for my purposes. It's no Janty Kissbox or JantyStick, but this is a different animal altogether. It very closely resembles a real cig, and the charging pack is the best I've seen from anyone. Just extremely high quality craftsmanship. The thing is gorgeous.
Battery life is good, a cart lasts me about two days, and the pack recharges a dead battery in a few hours, or less than an hour if hooked to a computer via a USB cord. I flat love the thing. So much that I loaned it to my son -- and he's been off real cigs almost two weeks now using the GreenCig G300!
I have no idea, however, where they are sold .. or where to get replacement carts/atomizers. Know this: These carts will not be refilled easily. I never succeeded, even using a syringe and attached needle. When they are empty, they get tossed.