Hmm. It's probably worth checking out the HTPC forum at www.avsforum.com to find out what the flavor of the day is. In my (limited) experiences, the 'best' player can be dependant on OS version and sometimes on hardware too.

It can get even more complicated - players comprise 2 elements, the decoders and the GUI. Most of the players today use directshow filters to implement the decoders. This means that you can plug and play various filter sets into a different UI. For example, in my HTPC I use Ravisent Cineplayer video decoders with WinDVD audio decoders using Zoomplayer as the UI. Zoomplayer is freeware from an Israeli coder called Blight, and is incredibly flexible and extensible. It will allow you to pick and choose your decoders, it plays nicely with girder (automation tool), it is skinable, it is _totally_ configurable. It doesn't come with any decoders though, so you will still need to buy at least one player to get some.