Homes HAVE to get smarter. The market dictates this. But up to this point, the cost to gain ratio has been far out of balance, not to mention the approach of poor quality touch screens and feature lists that read like a 1999 computer spec :) I agree nest is too expensive at $250, but I doubt that it will hold that price tag for long, partnerships are coming I'm sure.
It's a little like asking what made the iPhone different to the nokia of the day, or Dropbox to FTP. It's more about market timing, pricing and user experience than anything in a spec.
What else? Put bluntly; timing, founders and funding.