I have been thinking of writing my own version one of these days which works the way I think a bug tracker should work. For anyone who wants an idea here is how I see it working. Three columns, similar to outlook. The far left with projects/users the middle with issues and the right with details of the issue. A single search box which intelligently picks relevant issues/projects/users based on what's typed and instantly displays the results. Clicking on a project or user displays issues assigned to that user or project. Clicking on the issue displays the details on the right pane. Add drag and drop file uploads, instant comments and you have something I feel is already more productive then any bug tracker I have used.
I guess my biggest complaint is how hard it is to find bugs/issues in the system and jump between them. The above may solve that pain point. Its certainly a weekend project to implement.