I have to admit to being a jira lover inspired by http://news.ycombinator.com/item?id=3000200. With so many people posting polar opposite experiences, I wonder:
What issue tracker(s) are you using?
For what sort(s) of projects?
How default/custom is your installation?
How many other issue trackers did you try, if any?
As always, the "and why" information is nice, too.