Adding a network in wpa_gui does not preserve it between bootings? add to wpa_supplicant.conf:
and it will actually rewrite wpa_supplicant.conf each time you add or modify a network. (but any comments are lost)
wpa_gui can't access the socket so you can configure it, as an ordinary user? add this to wpa_supplicant.conf:
(then of course your regular user account needs to be in the wheel group, but that's quite useful anyway on Gentoo, as a rule)
The new version of wpa_gui even is integrated with KDE: when you close the window, it stays running in the "tray". This rocks!