If you're interested in the development being done on Nautilus (which is bring renamed to "Files" in GNOME 3.6), see these two blog posts:

http://blogs.gnome.org/mccann/2012/08/01/cross-cut/

http://blogs.gnome.org/mclasen/2012/08/30/on-nautilus/

See the post discussed at http://news.ycombinator.com/item?id=4465904 for more changes in GNOME 3.6.