Primarily a bugfix release.
Also themable email content, views integration and other minor enhancements.
Check access control settings when upgrading to this version.
Thanks to the hard work of many, Workflow is ready for Drupal 5.x. Special thanks go out to Pancho and swood for extensive testing and patching.
I would still recommend making a test update database, importing your old db into that, upgrading to drupal 5 (and workflow 5.x-1.0) and testing BEFORE running the update on your production boxes. I think workflow is very stable, but you have been warned. :-)
I think it likely we'll have a 1.1 release soon, as people start to adopt and test this module more heavily. Please help by testing, submitting bugs, and reading the bugs of others. I will consider your bug for earlier fixing, if I see you've commented on other issues in the workflow queue. I'm not kidding!