Some plugins are causing grief for those upgrading to 2.8.

• HyperDB needs to be updated to the latest version, otherwise tags won’t save.
• DB Cache also prevents tags from being saved. I haven’t seen an update for it yet.
• Plugins that load old versions of jQuery for all admin pages will break all kinds of stuff.  Plugins should use the version of jQuery that ships with WP.  If a plugin must use a particular version of jQuery, that version should be queued only for the plugin’s own pages.
• Themes that call get_categories() from functions.php before the init action fires will fail.  2.8.1 will workaround this, but ideally these themes should update so that they can handle custom taxonomies properly.

WP’s automatic upgrade can be used to automatically upgrade to betas and nightly builds for the development branch or the latest stable branch.  To get onto a development upgrade path you must first make a small change to wp-includes/version.php.

The current release of WP is 2.8.  If you peek in the version.php file, you will see this:

$wp_version = '2.8';

If you would like to try out the latest development builds for the upcoming 2.8.1 release, change that line to this:

$wp_version = '2.8.1-dev';

“dev” can be any string. The presence of a suffix on the version tells the automatic upgrade to put you on the upgrade path for 2.8.1 development releases. You will be able to automatically upgrade to each nightly, beta, and RC build for 2.8.1. Once the final 2.8.1 release comes out, automatic upgrade will upgrade you to that official release and put you back on the stable release path. To get back on the 2.8 development branch upgrade path after the release of 2.8.1, you would have to change your version to “2.8.2-dev”.

If you are feeling really experimental, you can get on the 2.9 development path by setting the version to “2.9-dev”. Unlike the 2.8 development path which contains only fixes to high-impact bugs, the 2.9 path is where new feature development is happening. You probably want the 2.9 path only if you are a developer.

Update: Peter wrote a plugin that makes this easier.

2.7.1 is out, improving upon a solid 2.7 release.

The next version of the iPhone app is almost out and features comment moderation.

2.8 is well underway.  So far there have been lots of script loading and DB performance improvements.  The first cut of the theme installer is in, and the redesign of the Widgets admin UI is beginning.  Custom tag taxonomies now have some built-in admin UI,  and proper timezone and DST support is available if you are running PHP 5.