Interface is really clear to understand and use and there is a lot of available configuration options. For instance, you can add multiple filters depending on user IP address or localization or a cookie value or anything else (User-Agent based, ...). You can also manage traffic of your website to be targetted by the test.
You can organize your different A/B tests easily (also group them) and you can easily enable or disable tests one by one via the dashboard page.
A big plus is also that a feature allows to preview your A/B tests easily so you can view them while developing new tests features.
Finally, you are able to view reportings of every A/B tests that really helps you to take a decision on each features you want to add on your website.
Sometimes the JS cache invalidation makes some time to take effects so you have to wait maybe 2 or 5 minutes to the A/B test to be updated.
Interface is great but as there is many options you have to take some minutes to well understand where are all the features you need.