One big item that almost all bug trackers is missing is a structured way to record "steps to reproduce". If you're logging a true bug, then the QA analyst and developer will need to reproduce it. But how? Sometimes, a bug only surfaces when the steps are followed in a very particular order. Change one step or move one action, and the bug "disappears", which gives rise to the infamous "I can't reproduce this", resulting in the bug getting put on the back burner. So tracking these steps is crucial.