I think the core concept of Trac is great: automatic linking between issues, wiki pages and revisions. I think it suffers from being slow and difficult to install and configure, as well as using a very uncommon rendering engine that has really stymied theming.

I use JIRA at work, and honestly it's completely fine. It's a goddamn bug tracker. If I can make bugs and close them it's doing its job. Nobody in my organization reads email or tracks their stuff anyway. Sometimes what you have are organizational/management problems, and no amount of wizzy technology is going to fix that.