I've also had three instances where upon rebooting due to a power outage or a system update, my inbound firewall / port forwarding was just broken. UniFi simply did not pass packets to my server. Once again, a full reboot of every UniFi device on the network resolved it.
I really want to like UniFi, and I appreciate how much access I have to SSH in and figure out what's going on (and I did take tcpdumps and have a support case open), but it has definitely not been plug-and-play for me.
I'm using a UDR7, U7 Lite, a number of managed UniFi switches, and just recently added the U6 extender.