The biggest speed improvements you get from Gentoo are the fact that the bare minimum of services tend to be running, just like you get on other distros like Arch and Slackware.
I think the biggest feature Gentoo has going for it are the USE flags. Setting up a couple of those during setup and leaving the rest out can dramatically slim down an installation compared to most distros which tend to compile in support for everything.
As others have mentioned, the compile times are no big deal. They usually take maybe 15 minutes a weekend, and while it's going you are free to do other stuff like surf the web, so you hardly even notice it. And they provide binaries for a couple of large projects, like OpenOffice. Upgrading KDE can take a few hours, and if you switch to a newer version of GCC you're supposed to recompile the whole system which can take all night, but those are exceptions and not the rule. More commonly I did have to spend some time every now and then merging config files and figuring out emerge conflicts. They're usually quite simple, but certainly nothing I would want to show the "average" user, who would be much happier with Ubuntu/OpenSuse/etc.
Oh, and you really should just use march=native now with gcc4.4. No need to try and specify the architecture manually.
Last edited by smitty3268; 01-04-2010 at 09:31 PM.