Doing split tests to understand the behavior of your visitors should be simple.

1. Define a test at the top of your page
2. Get the visitors current variation
3. Do stuff conditionally based on that variation
4. Track the visitor in Google Analytics

The PHP version of this script has been used in high-traffic production environments. It is by far the most stable of the bunch.

This ruby on rails helper should allow for simple tests at the view level.