It's relatively easy to use, and has a lot of functionality with regard to formatting wiki articles and embedding content.
Room for Improvement:
The search is pretty terrible. You can search for something that is quite close to text that appears in an article, and nothing will come up. I consistently have a hard time finding the things I care about on our wiki.
Overall it's a fine tool, but I don't think it provides a whole lot of advantages over other similar options. We use it primarily because we also use JIRA, and working with one vendor makes things easier.