The tool is based on GEGL and combines moving, scaling, skewing, rotating and adjusting perspective. It also has a long anticipated "From center" option.
Main features are already working except scaling. There are also some bugs to fix, and some UI changes to make.
The branch is now available in upstream Git repository: http://git.gnome.org/browse/gimp/log/?h=soc-2012-unified-transformation
No builds are available yet.