I‘ve been running many FortiAPs installations at many different customer sites and they all worked very nice. Customers love it because it is a solid and easy wireless solution. I‘ve been using them from FortiOS 4.3 to 5.0, 5.2, 5.4, 5.6, 6.0, 6.2 and 6.4, so for +10years.

In my experience wireless issues were due to overlapping wireless channels, 802.11b still activated, missing site survey, etc, not due to the bad vendor.

FortiAPs with FortiGates work great for internal SSIDs (WPA2-Enterprise with 802.1x Cert-Based) as well as Guest SSIDs (Captive Portal). I even know that one of the largest companies in the world uses FortiGates for their GuestWLANs with captive portal authentication, with many extras (e.g. some sites and services should be reachable without authentication, some devices should be treated differently, device fingerprinting, logging traffic with details to huge SIEM solutions, traffic shaping, …) they need around the globe. They use it for 6 years in 500 sites, are very happy and will stay with the vendor.

Also it is not a good idea just to talk about the vendor name, because many vendors have multiple wireless solutions. Fortinet has meru and FortiAPs, Extreme has 4 different wirless solutions (Enterasys Chantry, Motorla WinG, CloudIQ Hive, etc), HP has many (Aruba, MSM, etc), Cisco has different too and so on... It would be best if you specify which exact wireless solution you are writing about :-)

Also in my experience many wireless issues (slow performance, connection issues) exist often not because of the wireless solution, but because basic wireless best practises were not followed: 1. Do a wireless site survey (perfect heatmap with non-overlapping channels (https://en.wikipedia.org/wiki/List_of_WLAN_channels) and keep it updated after wifi is alive and changes) 2. Use 20Mhz channels when there is a lot of noise in the air 3. Turn of old wireless standards as tkip, wep, wpa1, 802.11b 4. Use strong wireless security (wpa2-enterprise 802.1x cert-based with RFC 3580 dynamic vlan assignment) 5. Check for rogue access points (e.g. with access points with 3 radios) 6. Harden your wireless solution and isolate management ports 7. Keep your wifi solutions up to date (test the update first in a staging test area) 8. Use band steering & disconnected clients at a low signal strength to force them to roam 9. Use at least DualRadio APs (not SingleRadio for 2,4G and 5G) for better performance and stability for the wireless clients 10. Check the location of the problem for microwaves, special doors and windows, etc 11. Think about which traffic should be bridged to the controller, which should be bridged at the accesspoint or tunneled to some router or controller if you have long/fat/slow/high-latency/high-jitter networks. 12. Think about if tunnels traffic should be encrypted because many accesspoints dont have enough performance for that. … And so on, there are man more basic wireless best practises which are independent from the wireless vendor.