I currently have 11 unifi ap ac pro units running in production at my company. I have 6 running at the HQ, 3 at the extension building and two running at remote sales offices coming across sonicwall vpn appliances. I am running the the controller under Ubuntu (My CTO is not big on RPM based distro's) without any issues thus far. The rolling upgrade works great and they perform just fine. We are currently running the 5.6 branch running on a small VM on my ESXI cluster.
We are actually looking into rolling out a pair of the AP's with the integrated PA speakers in the extension buildings since we need a intercom system. If we do I will post back about my results!