What do you like best?
Once a workflow is defined (properly), Trac can enable you to have a decent dashboard for looking at the current list of issues and priorities. It's extensible and has a built-in wiki component so you can put common project knowledge in the same place.
What do you dislike?
Trac looks, smells and acts like an engineering project. 10 years ago it looked like a 5 year old web interface. Today it's screaming not for a face lift, but a complete UI overhaul. (Apache Bloodhound?) It's far too easy to make a mistake with the overly cryptic process of creating ticket workflows, and when things don't work right it's hard to keep the team engaged in the tool, it can quickly create more work than it is replacing. ...that said, it doesn't forget like human do.
Recommendations to others considering the product
Don't spend a lot of time evaluating, if it seems clunky at first, it is.
What business problems are you solving with the product? What benefits have you realized?
bug tracking, milestone tracking, distributing work to members of a team, assisting to create reports