We just looked at the rather laborious process of reviewing many (maybe ten?) Problem tracking systems to replace GForge , which was getting in our way more than help. We looked at free and commercial systems.
To be honest, I was disappointed with all of the systems we reviewed. There are many opportunities for improvement in this domain.
Many of them had poor interfaces ( OnTime , JIRA , Bugzilla ). As a rule, our engineers were fine with this, but it is important that our project managers, system integrators and customers present an interface that is clear and aesthetic.
I was surprised to find that there is very little support for nested sub-problems. In the software world, of course, very often you have to break down a task (problem or new function) into smaller components and assign them to different people. However, most systems could not do this - or could not do it well.
Some systems were very powerful and customizable, but practically required third-party extensions or plugins to make them useful. I really liked the flexibility of JIRA and Trac , but we would have to spend considerable time setting up the systems to make them pretty or more functional.
Naturally, these are not the only functions with which we were associated, but this post is already too long!
Of course, your requirements will differ from our requirements - I urge you to find out what you need and carefully study it.
FogBugz , JIRA and Trac were on our short list, and they all had great features. But in the end, they were beaten by a product that was previously unknown to me: VisionProject .
VisionProject is attractive and provides a good balance between powerful and easy to use. The only drawback that we see at the moment is that their new interface (starting with version v4.0) Ajax-y was a bit of a mistake. Nevertheless, we had several corrections overnight, and sometimes within a few hours, in their team responsible for the mental reaction.
We are still testing the system and, although not perfect, we compare it with other rivals.