nvidia-kernel won't work with a vanilla 2.6.11, you'll have to wait for an ebuild for ck or gentoo-dev-sources
I don't think you are right here. gentoo-dev-sources is not patched with anything that would aid nvidia compatibility.
I think you might be right in saying that nvidia's own driver release doesn't compile against 2.6.11 (yet). But in portage, we patch nvidia's driver (nvidia-kernel) with fixes for this. Using the latest testing version of nvidia-kernel should be fine.
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