GF6200: I think that may have been my problem. I had tried using the FreeBSD AGP driver for both my laptop and desktop. While the desktop handled it better, I think I had stability problems with both. The desktop would eventually lock up while the laptop would panic right after glxinfo finished. Try using the Nvidia AGP driver.
GF6800GT: I think Nvidia changed the way the EDID code (and other stuff around DPMS) worked. For me, DPMS no longer works on my desktop. The screen blanks but the backlight of my LCD is still on. I have to turn the monitor off, move the mouse or hit a key and turn the monitor on before I can see anything again; it gets locked into that state.
I read (and hopefully interpreted correctly) that the acpi_video driver in FreeBSD should be better behaved in 7 (http://groups.google.com/group/fa.fr...1ddd0f1103d8dc
) since it will no longer be an all or nothing lock on the device as it is now. Currently, only acpi_video or Nvidia may grab the device.