My USB keyboard did not work during the CD install of Gentoo 1.0rc6r14. This was also reported by another user in message <F20K4xDh9vXsFFsAitV00005e60@hotmail.com> in gentoo-dev. [What component should the installation PRs be filed under?]
You can enable, with most BIOS', a type of emulation layer by selecting USB Keyboard support in the BIOS. A work around, but something for now.
In my experience, the BIOS-based solution only work at LILO prompt, and stop working as soon as the kernel is loaded.
The -r15.iso (being uploaded within the hour) includes full HID support which should solve this problem. Resubmit a bug if -r15 isn't working for you.
Just tested -r15, and it works fine.