This is about to be released and is available for pr-order. The thermostat is awesome, and this is worth giving a try. No live reviews yet, but some really neat specs to overhaul an ordinary home object that I have stored under the sink because they go off at all the wrong times (so I'm no safer at all). Read Jason Yang's great roundup of the Nest and other competitors here.
Nest Website with video
Engadget Review here.
Wired Review here.
(Image credits: as linked above)