Nest is a cool product, but it might be just slightly ahead of its time, by a hair. Maybe the future generation of homeowners will be adamant about having a high tech touchscreen interface for their HVAC system, but for most people I know, it isn't a problem they're compelled to pay for. As the saying goes, the existing solutions are generally "good enough". I think Nest is on to something, but I'd bet it's another 5-10 years before they start seeing real breakthrough success.