Pivotal Tracker is an interesting idea, and some people might find the layout and workflow useful, but for me it was just too far removed from the more "traditional" project and task manager tools that I'm used to.

My company switched to a solution called SuiteDash several months ago, and we have been very happy with the results. It has all of the project and task management functions we need, in a familiar and easy format. Also, SuiteDash has other useful features like client billing, file sharing, and CRM. We are able to run our entire business using SuiteDash, and we couldn't be more satisfied.