I use OpenELEC which is a distro specifically for XBMC.
I use it to playback from attached USB drive, or from my PC over DNLA (MediaTomb running on Ubuntu), or from my Humax 9300T PVR over DNLA. Works fine. I believe there are quite a few other features I haven't yet tried as well.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed. Here's an example...
“I own the world’s worst thesaurus. Not only is it awful, it’s awful."