Long time lurker here, finally having something to say
I've experimented quite a bit with anaglyph 3D and Warband. Nvidia's built-in driver functions are certainly easiest to get up and running, but isn't very configurable. It requires quite strong filters in the glasses to get rid of the ghosting, which ruins the effect a lot. Also, it can only output red/cyan anaglyph. Nvidia used to provide promotional glasses (Discover 3D) at various events, with filters presumably perfectly tuned to the output. Your best bet to get an acceptable effect without these is to get the cheap cardboard type of red/cyan glasses, as their filters tend to be strong. If you get the better quality plastic ones with acrylic lenses the filters are not as strong, and the result with Nvidia's anaglyph output is quite unacceptable. On the plus side, these glasses, which more or less conform to the "Anachrome" standard, allow better color vision through the filters, yielding a better overall experience with properly tuned imagery. Generally, they make use of more washed out red/cyan, with more emphasis on true color. Also, they don't work well if parallax gets too high, so there's a soft limit of how much "pop out" and "pop in" you can get. With training, this may increase - the brain needs to get used to it. Nevertheless, I recommend them over the stronger filtered ones. Something along these lines: http://www.rainbowsymphony.com/professional-3d-glasses.html
Now, to get good results with glasses like this and games, Nvidia's driver just won't do. Get IZ3D's driver. The anaglyph portion is free. It is enabled with a configurable hotkey, and supports various profiles for different games. For Warband specifically, I get the best results with "Optimized (Red/Cyan)", a convergence of 0, separation of 50%, and autofocus off.
Here's a screenshot.
The overall experience of playing like this for days is good. Your eyes get used to the weirdness rather quickly, and the addition of depth perception really does something for your accuracy in battles. The tradeoff is a certain loss of brightness (adjusting the monitor to compensate and getting the colors exactly right may be necessary, but IS possible with a typical LCD screen) and a certain but not complete loss of color.
Apart from gaming, it's fun stuff to play with if you do digital photography. If you have a stationary subject, all you need to do is take two pictures slightly apart - about 1/30 of the distance to the focus point, and then use one of several freeware applications to turn it into anaglyph