This is a summary of recent technology and site configuration changes that affect the English Wikipedia. Please note that some bug fixes or new features described below have not yet gone live as of press time; the English Wikipedia is currently running version 1.26wmf12 (f0490d8), and changes to the software with a version number higher than that will not yet be active. Configuration changes and changes to interface messages, however, become active immediately.
The file upload form now checks both the post_max_size and upload_max_filesize php variables, and uses the smaller of the two. (r50706, bug 18411)
If a user attempts to move a page that has semi-protection for moves, he/she will now see a semi-protected page move warning to remind of the semi-protected status. (r50701, bug 18466)
div tags with unique classes for each page have been added to watchlists. (r50714)
MediaWiki release candidate 1.15.0rc1 has been released. 
The "create a book" sidebar link has been removed for the Collections (PDF) extension, though the extension is still enabled and can be used via the Special:Book page. In addition to the "Create a book" link, the Collections extension also included an "Add wiki page" link, which was intended for users to add pages to a pdf/book collection. In usability testing , some confused that link for something to use to add a new page to Wikipedia. In the MediaWiki SVN, the link has been changed to say "Add page to book". For the time being, the collections sidebar is disabled on English Wikipedia, pending further discussion.