The third release candidate for WordPress 3.4 is now available. Since RC2, we’ve fixed a few lingering issues with the new live preview feature, as well as with custom headers and backgrounds.
There are no remaining issues, and we plan to release 3.4 in the coming days. But if you think you’ve found a bug, you can post to the Alpha/Beta area in the support forums, or file a bug report on WordPress Trac.
To test WordPress 3.4, try the WordPress Beta Tester plugin (you’ll want “bleeding edge nightlies”). Or you can download the release candidate here (zip). Be sure to visit 
→ About for an updated list of features and under-the-hood changes. As a reminder: We’ve published some resources on the development blog to help plugin and theme developers prepare.
The new live preview
Nearing perfection, and yet?
Not yet. RC3