One of my Nest Protect thermostats had a false alarm a month ago. I was traveling and my wife, alerted to where the problem was ("smoke in the office") turned on the ceiling fan there and it got happy. Probably some dust got in there? Hard to say. I'm not sure whether I should bug Nest to replace it or not. Other such incidents seem to happen now and again, at least based on what I see on the Nest chat forums.

So, yeah, I'll still count myself happy with my Nest Protects. I hope they invent some other way to shut them up in the case of false alarms. The hand-wavy thing is pretty cool. Maybe they'll shoehorn it into their app?