The majority of dual-layer discs include a lot of menu content and extras that invariably take up a large portion of the disc's capacity. A number of people I know rip all their discs and have kept me updated with these stats. In any case, REencoding to 2GB produces very fine quality for most titles as MPEG2 - as MPEG4 even better.

I haven't bought any Superbit discs and I'm pretty glad - HD content around the corner.

Bruno