A bit like you, I could find little concrete info when I ordered my Edition 30 last month - I was swithering over the Soundpack and RCD500...I've come to like the BOSE in my current TT and was looking at all the factory options for audio
My salesman admitted he knew very little about the soundpack...a bit of internet trawling confirmed that very few dealers knew much about it. I really don't think it will retain any value whatsoever come trade in time, unlike Audi, where BOSE does seem to be a definite plus for trade ins.
As far as I can tell, it consists of slightly upgraded speakers, and a separate amplifier to drive them. From internet posts, sound quality is not that much improved from the standard fit and not really worth the £400 extra compared to the RCD500 standalone option
I've just gone for the ipod interface and RCD300 with 8 speakers, and will probably spend a few hundred changing the speakers to better ones if I get annoyed with the standard fit ones