I tried the AMD64 version of ubuntu 6.01 and 6.10 and had graphics card problems. Its X.org doesn't work with my ATI X800 out of the box so I installed ATI's proprietry driver. That worked but it always hanged when I tried to shut down X.
Now I'm trying Suse 10.1 AMD64 and my graphics card works out of the box! woo hoo! And the ATI proprietry driver is rock solid stable.
The trouble I'm having with Suse is dependancy hell. I want to install FF2.0 and OOo 2.0.4 but I get dependancy problems including one that is just a number, very odd.
BTW What is the Gentoo graphial installer like? I think a stage 3 install with that would possibly be quite a good idea.