I bought one because it plays just about every audio and video file format you can poke a stick at (including Ogg Vorbis,FLAC and MKV

). And it comes with a program to convert those it doesn't (e.g.MOV) to a format that it does.
To my surprise, you can even plug an iPod into it and it will scan it and allow you to search and play artists, genres etc. Two USB storage devices can be connected at once.
The GUI is a bit clunky but better than I expected from the reviews.
Set-up is idiot proof. Most of the default settings are what most users would want anyway and changing settings is easy.
Happy to answer any questions.
Cheers,
Squash