What is the reason you're reinstalling? Are you upgrading to another PC? If so, I would set things in my make.conf and kernel conf so that stuff can run on both machines. Recompile, move everything to the new PC and from there remove the support for the old platform and recompile, which can advance with every update of packages as you move on.
And there is now a binary repository which helps speed things up.
I am personally not a fan of such install scripts, because I have chosen Gentoo to avoid them in the first place.