Really, honestly...tell me what percentage of people out their know that faking a MAC address is even possibile...or how many even know what a MAC address is??
Unless you live next door to a wily teenager or a hacker, I highly doubt you're going to have a number of people bypassing MAC address filtering.
Better to be safe than sorry is what I say.
Besides, keeping a MAC whitelist up to date can be a huge pain. It's just easier to set a good WPA password and be done with it.