Rated 5 out of 5 stars

Works as advertised, and is very useful. CSS selector support would be a great addition, as would the ability to insert an auto-completed (tab) word when pressing a separator like '/', rather than having to first press enter to insert the auto-completed word. Another nice feature would be an optional "auto expand all", particularly when operating with "Show Entire DOM" disabled. Keeping focus in the xpath textbox after hitting enter to eval is a nice touch, but an optional eval-as-you-type would still be nice to also have.
But even as it currently is, a great tool for working with XPath.

This review is for a previous version of the add-on (0.9.1).