GIMP 2.7.1 brings plenty of changes from user-interface tweaks to GEGL improvements to various internal core changes. The technical list of changes for GIMP 2.7.1 can be found within their tree's news file. For a more general overview of the GIMP 2.7 changes for end-users, see the release notes. Within GIMP 2.7 the user-interface is being significantly reworked, the projection code has been ported to GEGL, and there is a plug-in for JPEG2000 files, among other new features.
Downloads of the GIMP image editing/manipulation program can be found at GIMP.org.