I had a Nest thermostat in our condo unit that we rent out that had been working for years just fine. Got Alert to come in to service the existing heat pump (as it had stopped producing heat). I get a call from the tenant indicating that they will need to install a new thermostat (which I will need to pay for) because it had been improperly installed and coincidentally broke while they were servicing the heat pump. I found this a rather curious coincidence seeing as how it had worked fine for years.
More recently I had them replace the same heat pump. Not sure why I ended up choosing them - must be getting forgetful in my old age. As far as I can tell the replacement went OK. They sent an invoice shortly afterwards. Before the job started I had specifically asked them to ensure that the wiring was compatible with a Nest and to provide a wiring diagram and they said it was not a problem. When the invoice came, I asked about the wiring and the diagram and indicated I'd be happy to pay as soon as that was confirmed. Their accounting clerk copies Denny and asks him to respond. Nothing. So I wait. And wait. And wait. About 4 months later, I suddenly get a barrage of threatening e-mails demanding payment and tacking on 4 months of interest. I reply to each of them, again reiterating that I had been awaiting confirmation of the wiring and the wiring diagram and enclosing copies of the prior e-mails. Each time, they disregard my response and send yet another e-mail demanding immediate payment, or they'll tack on additional interest and service charges, and threatening to send it to "collections".
In other words, the folks got really upset because they didn't bother to respond to a simple e-mail to confirm whether or not the work that had been promised to be done was in fact done, and then forgot about it four months. Rather sloppy and unprofessional, in my opinion.
The heat pump seems to work though, so there's that.