Heads Up To Developers: WordPress 3.4 is in Beta

See the post on the wpdevel site:

 Here’s some of what’s new:

  • Theme CustomizerCustomizer Tool built into WordPress core that hooks into most modern themes. You can use it to preview and modify many of your site’s appearance settings. with Previewer
  • Flexible Custom HeaderHeader The header of your site is typically the first thing people will experience. The masthead or header art located across the top of your page is part of the look and feel of your website. It can influence a visitor’s opinion about your content and you/ your organization’s brand. It may also look different on different screen sizes. Sizes
  • Selecting Custom Header and Background Images from Media Library
  • Better experience searching for and choosing a theme

And some of the under-the-hood changes:

  • New XML-RPC APIAPI An API or Application Programming Interface is a software intermediary that allows programs to interact with each other and share data in limited, clearly defined ways. for external and mobile applications
  • New API for registering theme support for custom headers and backgrounds
  • Performance improvements to WP_Query by splitting the query (Please test!)
  • Internationalization improvements (improved performance and locale support)
  • Performance and API improvements when working with lists of installed themes
  • Support for installing child themes from the WordPress Themes Directory

Note: there are changes in WordPress 3.4 that will impact Themes, and the Theme Review guidelines. Now is the time to switch your development environments over to the beta version, and start hammering on the changes. (And if you find any bugs, report them!) Soon, the Theme Review Team will begin discussions regarding changes to the Guidelines. If you are interested in participating in those discussions, please betaBeta A pre-release of software that is given out to a large group of users to trial under real conditions. Beta versions have gone through alpha testing in-house and are generally fairly close in look, feel and function to the final product; however, design changes often occur as part of the process.-test now, and keep your eye on this site, and on the Theme-Reviewers mail-list.