I first gave Ray Camden's Lighthouse a try a few years ago when it was released on a DRK. I didn't end up using it at the time because I remember thinking that as my project grew the XML storage engine could become an issue. Since then I've used several commercial bug trackers including ProblemTracker and JIRA and currently my company is using a home grown issue/request tracking system.
Well, we recently started a fairly large project at work but I didn't want to use our in house issue tracking system as it generates several notifications and requires managers to route issues. While we will eventually move this project into our in house system, at this early stage of development it really didn't seem appropriate. So I decided to give Ray's Lighthouse another try, this time in the form of Lighthouse Pro. I have to say I'm really impressed. I downloaded the package and had the bug tracker up and running in less than 10 minutes. Best of all our team now has full control over our own bug database which should help speed up development and keep us from annoying everyone else in the company with all of our bugs. Not that we ever write any buggy code mind you.