Extremely capable masking app marred by a terminally bad DRM scheme that punishes legitimate users (transferring your license to a new disk on the same computer causes you endless grief). Updating? I'm not that masochistic. Well, after my third attempt I got the message that it hates me.
FM comes as a plug-in for PS and Aperture, and also as a stand-alone App. I currently can only use the stand-alone version because it refuses to co-operate with PS (did I mention terminally bad DRM?).
Another strike is the decidedly Windowsy interface - FM looks (and performs) like a WINE-based application.
Which is a shame, really, because few masking tools work as effectively as this one. If you do a lot of complex masking (especially hair other fine-detail work), you should definitely give it a try.