I built a new video editing rig and on my x64 Athlon, I installed Win 64.
I finally got my video working with an addition of a Parhelia 8X 256MB card. This can run all my 3 monitors at once. I tried for a long time to get my 3rd monitor running, but because of the unavailability of x64 drivers, I had to go the Matrox route.
It should take about a year before the other computer manufacturers to catch up with x64, but for the moment, I suggest one stick with Win32.