Hello,
I think we should start to maintain older versions of the API. I have therefore added a new page on MediaWiki wiki: http://www.mediawiki.org/wiki/API:Backporting. I have started by adding fixed bugs from RELEASE-NOTES to the page. I will probably start the backporting once I have time to find out how subversion's merge functions work. Feel free to add and remove items to that page or to start backporting yourself.
Bryan
mediawiki-api@lists.wikimedia.org