i use nmj since it was released on the C200, it was a pain in the beginning and totally useless when it came to Tv shows, also the missing multi language was crap.
I have currently an A-300 with the newer NMJ, on this i have no issues anymore, i have my music, movies and tv shows in nmj, the metadata is in my language now and it just works for me.
One important thing is that your library is correctly named, so naming like avatar.1080p.dts........ will not work, or you use nfo files then the naming doesn't matter.
My music is perfectly tagged, so also there i have no issues.
Anyway XBMC or in your case Boxee jukebox is for sure still more advanced, but i am fine what NMJ gives me and my family.
Yesterday in the nmt forum they posted new videos, maybe this helps?