It should get anyone on App Engine (python) up and running and A/B testing in minutes -- if you have trouble please let me know. Does its best to maintain identities as users transition from anonymous to logged-in, persists experiment results to the datastore in the background, etc.
http://bjk5.com/post/10171483254/a-bingo-split-testing-now-on-app-engine-built-for-khan
https://github.com/kamens/gae_bingo
Feedback/patches welcome