iTunes is great for music but sucks for vids.
I don't see what's so bad about WMP, i think people blow it out of proportion. With the k-lite mega codec pack it plays just about anything i throw at it.
I do use VLC for the ones that don't work but that's rarely, and the interface sucks.
KM player looks very similar to WMP. What's the difference and why do you feel it's better?