I'm glad they share their findings but would have loved to see more actual information in this 3 part series.

what about:

* actual signup rate (not only compared to before) * retention (that's the thing that really counts right?)

does anyone know good articles on a/b testing that cover the important things like statistical significance and how to make sure that the novelity of the change isn't skewing the results and so on? I fear that too many people fall into the trap of drawing premature conclusions and wasting time and money :(