I have recently upgraded my HTC One dual sim to Kitkat - latest firmware.
I also did a factory reset of the phone after the update
I am having problems connecting to certain routers via wifi - after some research i noticed that the problem occurs when the routers are set up to use WPA-PSK - as security. If you change this to WPA2 - the phone connects.
This is not much of an issue if i have asses to router settings - yet this is not the case in public areas.
I have sent an email to HTC on this - and i am still awaiting a response