I bought one 3 months ago (damn!) and am very happy with it. I can't say for sure I saved X dollars but between airwave, auto-away and it's easy scheduling (compared to my old, confusing, impossible to understand thermostat) I can't imagine it hasn't saved me at least some money.

But on top of that it looks good in my high traffic hallway. Being in the hallway to my bathroom it acts as a nice night-light (it turns on when I step out of my bedroom to goto the bathroom and visa-versa) and overall has been a joy to work with.