OmniFocus 1.6.1 is a free update which improves compatibility with 10.4, improves sync performance (and sets the stage for even more substantial improvements in future releases), fixes some attachment bugs, and updates localizations. For more details on this release, please see the OmniFocus release notes.
You can update to 1.6.1 by choosing Check for Updates from the OmniFocus menu (which will automatically update your currently running copy), or by downloading and installing the latest release from the OmniFocus web page. As always, we welcome any feedback you might have! You can reach us by choosing Send Feedback from the Help menu, or by sending email to email@example.com.