Hi,
this is just a (not so) funny request as I'm going mad trying to find a program that could be as good as MP3TAG is.
Right now I downloaded VirtualBOX and I'm going to install a XP vm just to run MP3TAG... 
Thank you Dano,
I thought it was a funny question...obviously it is not so funny.
Do yourself a favour and try puddletag. It's very intuitive to use if you're familiar with mp3tag, offers most of the same functionality (with some enhancements), is native to Linux and OS X avoids the limitations of running mp3tag under Wine (such as case insensitivity, inability to rename folders).
Info re getting it up and running on OS X can be found here.