With my Motorola SBG900 cable modem/router, I have WIRELESS SECURITY (Advanced Tab) set to "Allow Only Listed Stations Access" and MAC ACCESS CONTROL LIST turned on. Security Mode is set to NONE with no WEP or WPA (my choice for simplicity). This is the way I prefer it unless there's a real problem in allowing access by Mac Control List.
My feeling is that if the Mac list does the job, then why use WEP or WPA?
I live a good distance in the country and I doubt anyone would bother to get some free broadband bandwith so I'm not worried in that direction. But if there's any security issue I should khow about by not encrypting, login passwords, etc, then please let me know what or any other problems using only the Mac list.