Ignoring the fact the product didn't work for YC for whatever reason, the fact his experience with the company resulted in a negative tweet shows that their customer experience is a lot less than optimal sometimes. That's a problem.
I mean how bad can a thermostat be exactly to be classed as a "disaster". Did it explode ? Did it cause the temperature in the room to approach 50C ? Did it cause an electrical short that resulted in the wiring needing to be replaced ?
My support experience was well designed from the beginning when I did not need any human interaction where I just used the website. To the automatic support ticket generation that brought in human involvement and I had to replace of the unit.
At each support stage I found clear instructions for what to do as well as a smooth and clear path to the next step. Granted I am used to opening up my walls, moving around electrical outlets to suite my own tastes, but installing any thermostat is pretty easy.
From the tweet I can't tell if he could not get it installed or had issues getting it set up or issues diagnosing problems. Either way, my experience with the Nest product has been very different.
They sent me a replacement unit without billing me, giving me a month grace period to send back the old one. Turned out it wasn't the unit at all, but an environment issue (direct sun on sensor), that they then patched.