If you wanted to mod back to the old version, there're links on the Guitar Sticky about GT2. One of it links to a "build your own GT2" which apparently has comments on the differences between the old and new GT2.
Other than that, if you want specific tech stuff, go to diystompboxes.com and search the forums there.
The new GT2 sounds a little more sterile and modern to me. YMMV.