I have a fresh installation of Ubuntu 12.10 running on a new Dell Precision T7600 workstation. I four Dell 30" monitors connected to a single Nvidia NVS 450 using display port cables. I was able to get 12.10 installed and the Nvidia drivers configured with only minimal hassle. I was able to get a pair of monitors working in twinview but I was unable to configure all four.
When I moved to the four monitor setup, I configured each screen as its own xserver and used xinerama on top. I was able to see the background on all four screens and the mouse moved around correctly, but I was missing the dock on the left side and the menus at the top. I tried reinstalling twice (after debugging left my system unusable). I tried using Ubuntu's version of the Nvidia drivers, and the ones from Nvidia's website. I tried unity and gnome3 (the new version and the "legacy" desktop version).
Unfortunately I had to give up after two days of work and install RedHat 5.9. It works with my monitor setup, but installing Chrome has turned out to be impossible so far and my keyboard's volume knob won't work. I know these are minor things but please help me come back to Ubuntu!
I'm actually upgrading from a Dell Precision 690 with two Nvidia cards (QuadroFX 570 and 6200) running Ubuntu 10.04LTS. I ran this same monitor setup on the older system without a problem so I'm fairly sure my config within Ubuntu is correct is correct.