Additionally, it's pretty good at handling things when I'm not around to manually tweak things or something changes. If I'm off one day during the week it detects that I'm at home and doesn't fall back to the "away" schedule/settings and on the flip side, if I'm away at work or somewhere else, when I start my drive home, it can start heating or cooling early so the temp is where I want it when I arrive.
It's definitely a bit "gee whiz" but so far I've had no glaring issues with it but I've had several positive ones. My main feature request is the one you mentioned with the remote sensors. I'd love to see them come up with little night-light-sized "Nest Eggs" that you can plug into outlets in different rooms, maybe act as "smart" outlets for whatever you plug into the Nest Egg (my imaginary term, not a real product) in order to manage non-smart lighting or other minor appliances, and help build a more accurate heating/cooling model of the house.
If I was working at Nest that would definitely be the new product I'd be pushing for.
Maybe each Nest is a remote sensor, and everyone who has one has their house temperature set to the same temp, the result of some super-duper averaging algorithm running on Nest's cloud.
The only smart thermostat feature that's at all tempting to me is the Ecobee's remote sensors (which the Nest doesn't have). I've lived in places where uneven heating is a legitimate problem.