Free: Open source with Apache license. No plans. No limits. You can install it in your own servers.
Flexible: You have the complete source code in Java, based in OpenXava framework. So hiding features or adding new ones is extremely fast and easy.
Simple: Issues with title and type, no more is needed. Optionally you can use priority, project and version among many other things.
Worker plans: Define a period, like January 2020 or Week 32, associate the period to a worker, and you get the worker plan, where you can assign and order issues. More Info »
Customer and time: Manage your customers and assign a customer to an issue indicating the time expended in the issue. Useful to track customer support.