I use plex as my front end for my Intel based Mac Mini Media center on my 52" LCD in my living room.
As a medic center its great, i can seamlessly run 264x 1080P HD video and control the whole interface with the Mac Mini Remote.
HOWEVER its amazing for video/tv shows, but I find the music interface lacking and extremely annoying to use. I would not recommend this in a vechile just for this purpose it takes to long to navigate through all the music and decide what you want to listen too. This could be a major issue for me only because i have 150+ gigs of music, but at the same time, id have that in my car.
So my vote is NO for automotive use at this point. and YES for at home use. If your into home theater, id recommend looking into an intel mac mini based media center with a plex front end. its a beautiful thing.