Have used one since it first came out, with this suggestion: If you live by yourself, the only feature you will use is the ability to control it from your phone/workPC. I had to turn off the auto-learning feature, because it couldn't anticipate my erratic schedule in getting home and leaving, and I had to manually overide it almost daily. Had to go to timed programming (turning off the auto learning feature) which is equivalent to that of all modern electronic thermostats, which sell for under $100 at Home Depot/Lowes, etc. Now I only use it to get the heat/air going just before arriving at home, so it justifies my $250 cost (at least it is worth it to me to pre-heat/cool my house). The whole learning thing is a smokescreen, because it really can only work for fairly steady routines, and cannot anticipate erratic schedules, so if it really works, it is actually just like using daily timers on conventional thermostats.
One other note; if you own pets, and need to check up on the house temperature, it may be worth it to have the wifi access. I tried out another electronic wifi thermostat, but the internet connection wasn't as smooth as it was with the Nest, and most require you have a hot-wire to run the wifi portion of the unit - not so the Nest, which has its own built-in battery and ability to charge it without having this additional wire. This save a whole lot of money if you had to have an electrician run the other hot-wire; -- bottom line, it is more elegantly designed that any others just from an installation standpoint alone.
Perhaps Apple knows something about the wifi standards that are only now being talked about to control other aspects of our homes, and the industry's interest in standardizing them. That doesn't explain Apple taking it off the shelves, but it makes you wonder if Apple plans on taking the lead in pushing for industry-wide standards, as they have done in other areas.
Edited by Bagman - 6/23/12 at 6:09pm