I've used Trac in the past for projects. For my current project we have Jira and Confluence. Jira and Confluence are nice. However, trying to manage tasking for sprints is a pain. With Trac it was easy to create tickets representing tasking. Those tickets could be assigned to a milestone. There doesn't seem to be an analog Jira.
Confluence is a wiki, but integration with Jira is limited. Trac tickets can be referenced within it's internal wiki. When a ticket is closed it's displayed with a line through it. There are Jira macros for Confluence but it's not a nice as what trac offers. There's even an eclipse plugin for Trac to make it easier to deal with tasking.
We're going to examine the Greenhopper add on for Jira. Maybe it will make things better.