Otto's GIMP PPA now has builds for Ubuntu 11.10. So if you were waiting for these packages, just run commands below to install GIMP 2.8 RC1.
sudo add-apt-repository ppa:otto-kesselgulasch/gimpsudo apt-get update
sudo apt-get upgrade
sudo apt-get install gimp
Use this PPA at your own risk as it comes with no guarantees.
Thanks to Thorsten "Otto" Stettin