I wanna know that too.... though its written in many internet sites tht wmp12 is no better than wmp11
I use VLC( + quick time for 3gp etc) for all my media needs, Never had a need for WMP anyways except WMV files.
it also has difficulties playing some codecs like flac: seek is disabled and tags aren't shown properly
WMP12 is by far the best media player for Windows 7. Just install shark007's codec pack and it will play ANY format.