http://git.gnome.org/browse/gimp/log/?h=goat-invasion
http://gimpfoo.de/2012/04/17/goat-invasion-in-gimp/
They wrote a GeglTileBackend that uses a Gimp TileManager. This made porting surprisingly easy.

This will enable hardware acceleration via OpenCL, thanks to AMD's work.
And AMD should have OpenCL on both fglrx and r600g by the time this is ready.