I am using Windows 7 x64 ulti for the moment, but I dont load explorer, instead guide windows to load XBMC even before explorer loads, making it boot faster. How ever the idea of XBMC live is also not bad, but if you plan to use Live I will recommend another product based on XBMC live only, its called
Open ELEC. Its basically based on XBMC itself and acts as live as well, but is been customized to give a
better experience. I have tried it and I would definately suggest it above XBMC Live!.
About BluRay..... are you asking about Bluray ISO or Discs, for Disc I actually already have Pana BD60 BD player. For ISO I use the combination of Virtual Clone Drive and Total Media Theater5. A small script tells XBMC to mount the ISO in my drive and TMT5 to play it, so that I get for HD audio. Checkout my video.
Yep I have the subtitle and lyrics plugin. Radio I havent tried yet, but will definitely give it a try