I tried the driver on my FreeBSD 4.8 box, and it didn't lock up like it did with my 5.0 box. The thing is though, I use KDE, and with the nvidia driver, Konsole would always seg fault on exit, where it never did that with the nv driver. I could live with that though, so long as I could play some GL games. So, I installed the tuxracer package to check it out. Never could get it to play, because it would always segfault at start.
So in short, on my setup at least, it works in the sense that it doesn't lock my comp up, but it doesn't work in the sense that I still had no 3d support.
Nvidia had good windows drivers, but I'm going to avoid their BSD drivers like the plague.