One tool to do everything: Bug tracking, agile management, code control, code reviews, test management, delivery, continuous integration, etc.
And all integrated together (delivery linked to requirements for example) is unique in the world!
I'm very surprised by the bad comments... I assume the bad comments related to the database scheme is because the person did not understand the concept behind Tuleap. The high flexibility and ability to customize Tuleap Trackers implies a meta model for the DB. You do not see the actual or direct data you use in your bug tracker for example.
To access to the data, use the REST API. It is fully documented and very practical. No need to write embedded join queries. The API does it for you ;-)
AFAIK, Tuleap is also a tool which is used by large companies with thousands of users on a same one platform. This seems to be pretty efficient regarding CPU usage.
Tuleap is open source.
User interface is perfectible.
Contributors say they are working on it though. And the latest changes shows it goes to the right direction.