i remenber i had to reboot last time one controller in High Avality 2 3400s...
And i did it live when users were using the wireless network an a not peak hour.... we didnt recive any complains...
Take in mind that these users are not users which were using Wifi for Voip or HD streaming or anything like that.
They use the Wifi for internet access or to access internal apps
Cheers
Carlos