Can I just throw in a vote for this too?
I have a Synology NAS holding ~500 films and a hodge podge of TV eps from different seasons across about 80+ series. I need to get some 3TB drives and get the rest of the TV back off the hundreds of DVDs :-)
This is now also holding a MySQL db for xbmc, which is being used by;
my Win7 PC
my Mac Mini w/ projector
my flat mates iMac
and hopefully a new box on the TV in the lounge
I'll be honest guys, it was a billion miles from easy to set up, and I run the Infrastructure team for a UK hosting company. I should know what I'm doing (I don't, a lot of the time

) but I had to read a ton of stuff. Took me a whole evening to work out which way I should do it (MySQL? symlinks?!) and implement it.
My Mini and proj were in a cupboard since early 2009. I decided they needed to come out and prayed the OS X HTPC situation was better! From my experiences with MP before, I knew it was Win only, which didn't suit. Finding xbmc ported was great, but Plex has a lot of the answers too...
Here's my thread on why I'm still an xbmc user, but if they fix some things one day, maybe I'd switch the DB at least:
http://forums.plexapp.com/index.php/topi...-reaction/