I’ve packaged up WordPress 3.9 RC1 and intend to ship it Wednesday morning. For a complete list of the 33 issues, please see this report. Some highlights:
- Widgets: Theme preview empties sidebar on active theme. #27897.
- Multisite: Fixes regressions with uppercase characters in network paths; and with www as a subdomain. #27866, #27927.
- Header images: Fix weird behavior (or hiding) of various buttons: #28046, #27848, #27936.
- Performance: Fix potentially slow query on the new/edit post page. #27985.
- Various playlist, media, and editor fixes, including drag-and-drop text (#27880) and positioning of images when adding a caption (#27922).
- Some minor internationalization and RTL issues, like #27924 #27893 #27845.
Note this does not address a number of other issues, which are slated for a 3.9.2 release. Notably, many of these will require updates to TinyMCE, or require additional study or testing.
Download it here (zip) or grab the latest nightly (here or using the WordPress Beta Tester plugin). Testing strongly encouraged; feedback welcome.