If you're willing to do a little work on your side, you can craft a URL that will guarantee that the user ends up in a particular bucket.

One of the features that we're thinking about is doing visual diffing on A/B test variations. Then you can page through your variations and quickly see how they're different from the control, or if they're broken on any browsers.

To do that we would need a deeper integration, either with the user or with the A/B service. I think it'd be pretty cool though!