Gnome-2.10 has been in package.mask for almost two days with no huge problems so far. Thanks to people like latexer and foser for catching bugs early and reporting them.
For anybody interested in testing(normal common sense for running package.mask applies), just unmask and have fun.
sed -n '/Gnome-2.10 mask/,/End of gnome-2.10 mask/p' /usr/portage/profiles/package.mask >> /etc/portage/package.unmask
check this list before reporting any issues.