Oh, and if you used nvidia-installer from www.nvidia.com, then you're
probably screwed unless you want to put in an unneccessary amount of
effort to un-screw things.
Not true at all. All I use are the installers from nvidia.com. The installer will install the 64bit driver and libs and the 32bit libs. All you have to do is make sure the symlinks are ok in /usr/lib/ and make sure the libglx.so extension is the one from the installer. It really isn't that hard to do. If you have a basic knowledge of ln and know how the libs should be setup it only takes 2 or 3 minutes to use the installer and have a perfectly working system.
Quake 4 works fine on my amd64 box.