I work for a company in the secondary education financial aid industry in Des Moines, Iowa, USA. I just finished up a year-long project where we used HtmlUnit to do acceptance (user-level) testing. HtmlUnit was able to cover 90% (ballpark guess) of our test scenarios. The other 10% either required manual tests (for various reasons), or required enhancements and bug fixes to HtmlUnit. I didn't intend to learn the HtmlUnit code base when I started the project, but I ended up becoming quite familiar with it over the course of a year by filing many 
Bugs, Patches and RFEs.
You can read a little more about me on my SourceForge profile (see the Skills Profile) or on my Advogato page (which is a bit out-dated). I haven't had time to put up any content on my home page, yet.