Yesterday I downloaded latest drivers for my Radeon 7000 64 MB DDR PCI card, it is installed as my secondary GPU card and my primary GPU is my GF3 Ti 200 64MB AGP. Before the driver updates for the ATI PCI the two cards did not play nice together. I was constantly getting system freezes almost as soon as I started using the secondary monitor. Now everything is humming along with no problems. Not one freeze up since the drivers update.
Our friend was correct when he said that good PCI cards are getting hard to find so if you can afford it, after trying multimonitorring for a while and you decide you like it or not, you may wish to pick up a good PCI card before they become impossible to find.
Anyway, have fun.