This service is fantastic, they have the best recordings that I've seen so far (I've only tried ClickTale and Mouseflow). Unlike some competitors, they seem to record actual HTML that the user sees so it works well for very dynamic, user-customized pages. The dashboard is really easy to use and have some nice features like "rage clicks" or search by CSS clicked.
I love almost everything about Fullstory. The only problem I have with their product is that it's expensive. It has the feel of a young product with a lot of potential. I would recommend giving them a try. You may hit limitations in your ability to drill-down or filter, but you will immediately gain insight into what your users are doing on your site.