Here are a couple of fixes you might want to include in the next release to avoid throwing "deprecated" notices from your plugin.
widget.php line 8
Error: Use wp_register_sidebar_widget() instead. Deprecated in version 2.8.
- replace register_sidebar_widget with wp_register_sidebar_widget
inc/admin.php line 7
Error: Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead. Deprecated in version 2.0.
- replace the 10 constant with 'manage_options'