Very feature-packed, but the ways those features are implemented are hit and miss. There are a bunch of required fields in the registration process I wish I could customize or remove, though I can't complain too much about a free plugin. The HTML output is atrocious, not XHTML or HTML5 compliant and full of inconsistent syntax and inline CSS. In general, the code and UI are overly complicated. This plugin could be really great with some code cleanup and UI design finesse.
Also, a couple of times when submitting changes in the admin a DB error was thrown and all data for that section was erased. I can't tell if it was a WP or plugin error, but since the problem was isolated to this plugin it gives me serious doubts as to its stability.