You bet it is!!. Headway 3.0 and WordPress 3.3 work perfectly together! We always develop and test with the latest versions of WordPress. When the WordPress Core Team releases a beta, we immediately switch to the beta to continue developing and testing on. This way we make sure that our theme is working with the next version of WordPress from the get-go.
If you have not made the plunge to update to WordPress 3.3, make sure to take a few minutes to backup your site before you upgrade to WordPress 3.3. We recommend BackupBuddy for all your backup needs.