Manage versions and builds. You can keep track of which version/build a specific issue was found in and in which version/build the issue was completed/resolved. If you use resource management, you can also see summaries for time and money for the version, as well as how many hours users are assigned to work on the version.
By using the Estimated time and Remaining time fields on issue you can always see how healty your project is. You can easily edit estimated times and remaining times for issues included in a version and gets an updated Burn-down chart.
Automatically created release notes when an issue has been completed. Well, the text in the release notes is not automatically filled in. It is up to you to add a text to an issue if you want to have the text in the Release note.