I worked with a team that insisted on Pivotal Tracker and aside from its crashing my Fluid SSB every half hour or so, the text areas were way to small to type in comfortably. I found myself having to write the story in a text editor then pasting it in to PT. With that columnar layout, it just seemed like everything was cramped into spaces that were just way too small. Plus it doesn't track the history of a story. If it was assigned to Joe, then Larry, then Tom, there's no history of that chain of ownership.