Various places are reporting that nVidia have released the first 64bit Windows drivers to be certified by the Windows Hardware Quality Lab team.
I’m not entirely sure exactly what the WHQL certification means aside from being able to just install the driver without having to put up with the nagging dialogue asking you if you really wanted to install it - nVidia probably get to put a sticker on their products proclaiming them to be 64bit compatable too.

Of course, being stuck with an ATi graphics card, I cannot report on how these drivers perform, but I certainly hope that certified nForce drivers are next off the line.