The complete changelog back to version 1.0 is in the plugin code. Here's the changelog starting with v2.8 of the plugin:
- Fixes the "multiple widgets" problem caused by the developers' changes to the API in WP 2.8
- Now includes its own copy of magpie, since WP is moving toward simplepie
- Relies entirely on independent rss caching, not magpie's caching
- REMOVED the ability to call this plugin manually from a template. MUST be used as a widget.
- Minor bugfix. Oops. Saves correctly now.