I'm curious what you find so interesting about it. I've had an Ecobee thermostat (http://www.ecobee.com/solutions/home/smart/) for years and have even done silly hacks with it like integrating it with my wireless access point to detect when I'm home (http://jcs.org/ecobee) and making a SiriProxy plugin to be able control it with an iPhone (http://flic.kr/p/aNuGaF).
But even before the Ecobee, programmable and even WiFi-enabled thermostats have been around for many years and they have not gained any significant traction. My dad owns an HVAC company and they've only sold 1 or 2 Ecobee units in the years they've stocked them, with most people just opting for a schedule-based programmable thermostat.
What makes the Nest so much different? Is it just that it's pretty? Right now, their website says it costs $250. For the average person, that's probably at least a few years of energy savings needed to justify that cost.