Our main headquarters is spread over three buildings. I have implemented FortiAPs at two of the three. I also have installed them at our two remote offices. These provide wireless for all users in the office. I also provide a Guest SSID for visitors which is segregated from our main network - Internet only. This devices provide excellent coverage for all my offices. I have not heard one complaint about them since installing them. I also have the ability to monitor traffic on these devices and see who is doing what. I haven't implemented the various built in features (AV, Malware, App monitoring) as my Fortinet firewalls take care of that aspect for me.
New deployed AP - laptop could connect but mobile devices could not. They would connect but almost immediately lose their connection. Logs showed a true connecting but then an almost immediate disconnect. Worked with support for about a day to figure out issue. Support stuck with me and escalated the issue as needed. After firmware upgrades and some swearing, we were able to determine the issue was the switch that the AP was plugged into - it was not allowing mobile data traffic to connect to our DHCP server. Once we removed the offending switch, and replacement (by chance I had a spare Fortiswitch) traffic flowed just fine.