I know the answer for WPA is "not very", but here's the issue. Using phone company dsl wireless access point. Mixed environment with intel imac, g4 imac, emac, dell and toshiba laptops and an airport express for itunes. Ran into repeated connectivity issues (dropped connections, having to reboot the router, etc.) until I dropped down to WPA. So, on a hidden network, with WPA, and phone company firewall, how hard is it to crack from the outside? I'm in a rural area (only 6 access points showing up for wifi) so that reduces exposure somewhat.