Not too long ago, I posted an entry about MAC Address spoofing
(in Windows) via SMAC. I found a download for Mac MakeUp
a week or two ago and totally forgot about it until yesterday. I decided to give it a try and must say that the results and clean interface were quite efficient (if not less than 100% functional on all options). Give it a try if you don't already use SMAC or simply want an alternative.