The new radio buttons are now enabled (along with checkboxes) in the latest WebKit builds. Radio buttons behave as checkboxes do, meaning that they wont respond to properties like background-image or border until you disable the
-webkit-appearance property. Once you do, you’ll get a completely blank slate and can define how all the states of the control should look.
I also did some cleanup on radio buttons to make them more consistent with WinIE and with OS X as far as keyboard navigation goes. The radio group is now a single item as far as tabbing is concerned, and the arrow keys can now be used to navigate within the radio group itself.