RT is a battle-tested issue tracking system which thousands of organizations use for bug tracking, help desk ticketing, customer service, workflow processes, change management, network operations, youth counselling and even more.
Request Tracker is a no-frills bug tracker software used by the Perl community (the tracker at https://rt.cpan.org is used by most Perl packages on the CPAN). The tracker won't win any design awards (it's not particularly pretty, it was made by engineers for engineers) but it works reasonably well for what it does. You open bugs, add comments, subscribe others to bugs, etc.
What do you dislike?
It's an older technology and lacks the sort of integration with version control systems that users come to expect.
In many cases, GitHub Issues may be a better fit (it's nice to be able to reference issues in your commits and have some basic integration between the two - e.g. "Changes foo, bar, qux. This addresses issue #42" -- the Request Tracker doesn't provide this sort of integration.
It works pretty well for what it does. Its use for basically all distributions on CPAN ensures that it can scale to a large number of projects and issues.
Recommendations to others considering the product
If you're comfortable with Git, look into solutions like Gitlab and GitHub or GitHub Enterprise. These provide better integration between the version control system and the issue tracker.
What business problems are you solving with the product? What benefits have you realized?
I'm a published CPAN author (JAWNSY), so I use Request Tracker for my distributions as it predated the popularity of GitHub and is the de facto standard bug tracker for CPAN authors. I use it for keeping track of bugs as well as to-do items, there are usual fields like Owner, Cc, Severity, Dependency links, etc.
* We monitor all Request Tracker reviews to prevent fraudulent reviews and keep review quality high. We do not post reviews by company employees or direct competitors. Validated reviews require the user to submit a screenshot of the product containing their user ID, in order to verify a user is an actual user of the product.