I have used Stella for Mac OSX for a long time, truly awesome, two thumbs up!!
however, my MAME collection is crippled by MAME OSX now, hardly half of my ROMs work on it (that I played on older WinMAME versions many years ago), I had a different version called MacMAME that was much better but doesn't work in the new OSX LION so I'm stuck with the bad one, updates please!!! i refuse to install Windows just go get WinMAME on my Mac - not worth it