Before releasing a new package, you need to write the release notes in package.xml. The release notes should clearly say what has changed in comparison to the last release, or - when going to the next stablility level, like from beta to stable - list the changes since the last release of the same stability.
You probably want to outline new features, as well as list the bugs which have been fixed. It is important not only to plainly write down the bug numbers, but also the bug titles. People tend to recall words better than remembering the issues associated with a number. The PEAR web interface automatically links structures like "bug #<number>". In case several people fixed patches, the user's handle can be appended to the message.
Example 24-2. Bad release notes
Example 24-3. Good release notes