Amusement du jour: got home at the Nest had an announcement on the screen that it had detected insufficient movement over the past few days to be able to confidently run its "auto-away" algorithm. (It's positioned in a central location. If it has roughly the same hardware as a standard security system motion sensor, it should be able to figure out when we're around.)
At this point, the #1 missing feature, so far as I can tell, are nerdy things. I'd like the display to be able to show me the various sensors as they're working. I'd also like the web interface to be able to graph things over time, like temperature or humidity. I assume the data is in there, somewhere.