1) HA intercontroller heartbeats trigger failovers too readily and will be fixed in 6.4.2.1
2) Hospitality (wired-AP) ports after an HA fast failover die for 5 minutes, also will be fixed in 6.4.2.1.
3) 80MHz in especially in dense environments on the 225 causes false radar events (to be expected) but the APs occasionally go rf-dead (nearly no beacons sent) after getting one of these. Probably not fixed by 6.4.2.1 unless a fix occurs by accident, which does happen sometimes. We went deep with TAC on this one including debug AP builds. This
one is especially painful to OSX which hear the occasional beacon and associate but
then get stuck somehow and never roam off the AP until they move out of the area,
all while the AP continues to serve other clients. So it's a client-specific deadzone.
4) ARP spoof protection triggers on corrupt packets and blacklists clients. This happens almost only to iPhones. Unsure where the corruption is happenning. Not sure when the mis-triggering issue will be fixed. Worked around it with local-proxy-arp feature which pretty much eliminates the problem unless Apple decides to start sending too many unsolicited gratuitous arps.
5) A few mystery performance issues we know are there but haven't got anything to go on
but hearsay at the moment.