What do you like best?
Redmine offers many features for the cost and is extremely stable. It's designed well for management of small to medium size projects. With the right technical expertise, it can accomplish a lot for you. We've used it for more than five years. We used it in the role of service desk support as well. It integrated seemlessly with our organizational LDAP authentication system. Setting up the creation of tickets, and commenting, via email was pretty straightforward. Two other departments in addition to our technical group, have been using it as well. Those were both customer service groups and they were able to adapt to it with only a few hours of training. Customizing ticket statuses and workflow is simple and easy-to-use. As our group and scope of work have grown, we are now transitioning to JIRA.
What do you dislike?
No so much of a dislike but it base design isn't as flexible as commercial tools. The UI/UA design is easy-to-use and simple but not easily manipulated out-of-the-box. Setup of Ruby and Rails requires expertise in that environment. It's not as flexible for use as a Support Desk application. The administrative interface is not as refined and does not offer as much functionality as some other tools.
Recommendations to others considering the product
Redmine requires knowledge of Linux and Ruby on Rails amongst your DevOps team. I would carefully consider your project management and service desk requirements. It works best in the former role.
What business problems are you solving with the product? What benefits have you realized?
We needed track tickets for both our application dev projects and support desk. Redmine has worked well over the last five years.