Here's the problem -- you're throwing a lot of user data away. Are you saving the mouse position every mousemove or click? Are you continually monitoring if that page has focus? Are you turning on the videocam to see where they're looking at, if they haven't turned away towards something else?

A/B testing could work, with enough similar page widgets and enough data, but people need to collect orders of magnitude more data.

If you are going to A/B test in that manner or with Google Web-optimizer, you need to be aware of how your tests are setup.

There needs to be a clear and measurable action such as a sale to determine success. However, this is only a piece of the puzzle for most online sites. There are many other goals such as user retention, enjoyment and approval.

That A/B testing can be adequate for something like a sales page (37 signals testing was a good example), but falls short if you don't have clear measurable goals.