Firefox 1.0 PR1 considered itself "0.10" so if you install Firefox 1.0 RC1, you will discover that Firefox no longer considers the extension to be compatible. In my quick tests it really is, though. You should be able to use the Update feature to inform Firefox that the extension is compatible without needing to download a new version.
This feature does not appear to work — at least it didn't with my version. Firefox indicated that it thought they were compatible but didn't actually run them. If you find that you can't use the extensions even after updating, then simply reinstall them. This will ensure Firefox is using the updated information indicating that they work with Firefox 1.0.
The current XPI indicates that the extension is compatible with Firefox 1.0, so you should be able to download it without any issues.