Note: Flip4Mac does not yet work with QuickTime X on Lion. Lion users must downgrade to QuickTime 7.6.6 which supports plugins such as Flip4Mac for it to work.
Firstly, don't be misled by the name. Flip4Mac isn't a player - it's simply a collection of codecs which, when installed, allows QuickTime 7 and QuickTime based players to play WMV files. Flip4Mac is officially endorsed by Microsoft and allows you to play, import, and export Windows Media video and audio files on your Mac using your favorite QuickTime-based applications. This includes iMovie, Final Cut Pro, MPEG Streamclip etc.
The most important function for most people however is that it enables you to watch Windows Media in QuickTime 7. Note that it does not yet work with QuickTime X in Lion - user must downgrade to QuickTime 7 in Lion in order to use it. It also allows you to play Windows Media using the Safari Web Browser and import Windows Media for editing or conversion to other QuickTime formats. Unfortunately however, iMovie 08 and iMovie 09 are not supported.
The recent incompatibility problems of Flip4Mac WMV Player with Lion mean that it's not quite as important as it used to be and many users will find Perian a more powerful solution.
Flip4Mac WMV is still a powerful component for Mac users that need to watch Windows Media related content.
