a) hooray!; b) nvidia-settings
I must say, "Hooray!" ... I can now run FreeBSD in amd64 mode and have acceptable video performance!
However, I must next ask: what about nvidia-settings for amd64?
Just as a data point, I'm running a Core-i7 with 6G of RAM and a 275-GTX. I havn't tested a lot of things, but native apps like glxgears and whatnot work fine.
I've been trying to get steam running with wine --- but that's a challenge for an entirely different forum.