The update brings bug fixes and stability improvements
Opera is getting ready to push the latest minor update to the desktop browser and has now made available the first release candidate for Opera 12.13. Opera is moving quite fast since it was only a week ago that the first snapshot release of Opera 12.13 was made available.Since it's such a minor release, there doesn't have to be such a long testing period it seems. The RC comes with the obligatory stability fixes, without which Opera wouldn't be putting out a release candidate.
Also in this release are improvements in the performance of the address field drop-down and fixes for images on sites that rely on HTML5 History API.
Opera 12.13 promises some performance improvements, specifically to saving preference and web storage files. This should be most noticeable on sites which use a lot of storage data, such as Twitter, or extensions.