VLC plays back a lot of stuff, but I haven't experienced it being able to play back anything, other than full DVDs, than MPlayer doesn't handle. It also has a terrible UI and really bad (some non-existant) default key bindings.

I use MPlayer (used to use X nor pretty much always use Extended) most often and don't have any issues seeking in any file unless the file is damaged.

I don't play back any WMV content. For me, WMV might as well be betamax. It really doesn't have great support anywhere. When I encode myself I will now usually use x264 (H.264) inside an MKV.

QuickTIme player sucks, even with Perian, so I don't usually use that exept for look at the properties of a video file - since MPlayer and VLC show jack-all about the content being played.

I'll be giving Movist a try, thanks for the info Bitt. I've always recommended MPlayer (X or Extended) to everyone else, maybe this will change now.