I finally got this video board working on my old Ubuntu system. Here's how I did it.

Overview:

I shut down, installed the board, and booted. Ubuntu booted and ran in high resolution - very nice, that's more than Windows did - using the open source drivers. I went to "Software Sources", clicked the "Additional Drivers" tab. It showed 3 different versions of the NVidia proprietary driver I could use, or the open source drivers (which were already in use). I selected "nvidia-current", then "Apply". It ran a bunch of "apt-get" commands, built a new kernel, and completed with no errors.

Symptoms:

Desktop apps worked fine. glmark2 failed to run, generated an error message. glmark2-es2 ran very slowly. Steam crashed "Xorg" on startup, killing my session and logging me out.

Diagnosis:

I found several possible solutions.

One said to put a sleep in /etc/init/lightdm.conf just before it calls "exec lightdm" to give the GLX portion of the driver time to load. That didn't work.

Another said to install the driver manually via apt-get commands. That didn't work.

I tried a different version of the driver, nvidia-experimental-310. That didn't work (though later when I got it working, I kept using this version of the driver).

Then I read the /var/log/Xorg0.log file. This had a good clue. It said: "failed to initialize GLX module". Earlier in the same log file, it showed a message indicating it had loaded the open source version of the GLX module. Normally, that would be OK but since I was using the NVidia driver, it should have loaded NVidia's custom GLX. That was the problem I needed to fix.

Solution:

First I found the various GLX modules available on my system:
find /usr -name "libglx.so" -print
/usr/lib/xorg/modules/extensions/libglx.so
/usr/lib/nvidia-experimental-310/xorg/libglx.so

So the module was there, it just wasn't being loaded.

Next I edited /etc/X11/xorg.conf. There was only one ModulePath:
ModulePath "/usr/lib/xorg/modules"

I put the NVidia one in front of it:
ModulePath "/usr/lib/nvidia-experimental-310/xorg"
ModulePath "/usr/lib/xorg/modules"

This fixed the problem.

The NVidia Quadro 600 is a good graphics board. It's smaller, quieter, and consumes less power than the old Radeon board I had before. It has stable, fast drivers for Windows and Linux. It's about 20x faster than my old Radeon board, in both Windows & Linux. For example I can play all games in native 1920x1200 resolution with fast, smooth frame rates. That includes Trine 2 !

It's wonderful to see companies - both hardware and software - supporting GNU/Linux. For the first time ever, graphics intensive games run as well on Linux as they do on Windows. This will free both developers and users from the constraints of closed source proprietary systems. It will also make it easier for developers: write to one open source common platform, Linux + OpenGL, and your stuff will run on a lot of machines, and it will be easier to port to other systems like Android and variants like Ouya.

I'm impressed with Steam. They have a good selection of high quality games, low prices and frequent promotions, and whatever you buy you can run on as many different platforms as you want. Buy a game you like one time. Then download and run it on Windows, Macs and Linux machines. It also synchronizes your game status/progress on their cloud. And it has a "big screen" mode to play on your home theater. It's a great idea and they've implemented it very well.