I have started using them. My only reservation is when they decide to fail on an upgrade. However, when upgrading the APs, if they fail to upgrade they seem to always reboot and remain on the firmware they were on prior to running the upgrade. I would use these over Netgear since Netgear doesn't have a console port on most of their switches so when the upgrade fails, it generally becomes bricked. A service call can't fix a bricked Netgear; only advanced replacement can. The sad thing is that they publish firmware updates on their website and those fail.
I do like the setup on the Unifi controller for them. My only complaint is that I would like to name all ports and setup all ports from one screen and then click apply. I don't like having to go to each port and set them up individually from the GUI. I believe the release of these smaller switches in the Unifi and the EdgeMAX series will help replace some of the ToughSwitch Pro Switches.
I would never install the Unifi controller on a PC unless it were a server that is regularly maintained. I host the controller via Digital Ocean but it seems the cloud key is a nice unit and a decent alternative. Since I already have the DO setup, I don't plan on switching.
I do think they need to integrate 2FA into their controller for better security though.