A couple cool details. You can now "nest" gig files, allowing one to pass the 2GB file size limit. There is one gig file that simple points to sub-gig files.
Also, it sounds like you can make a gig with the sample set is in one file and all of the programming information in another. The time needed to save files should be really quick. It also seems like it would be possible to make a variety of gigs with them all pointing to one dataset, giving lots of variety with little wasted disk space.
What else? A more realistic pedal model using resonance rather than samples. And easy movement between 24 and 16 (or whatever) bits. A 12-bit option might be killer if it lets us load more samples into RAM. Compose at 12-bits, then refine/mix/render at 24. It could make for a great sketchpad.
Anyway, it sounds like Michiel is sold on GS3, though he targets all of the major platforms.