Important: The PPA below provides GIMP 2.8 final for Ubuntu 12.04 Precise Pangolin and RC1 for Ubuntu 11.10 Oneiric Ocelot (the final GIMP 2.8 for Ubuntu 11.10 will probably follow shortly) and while the packages in the PPA worked just fine in my tests under both Ubuntu 12.04 and 11.10, the PPA description says that there are some dependency issues, especially for Ubuntu 11.10, so use it at your own risk!