For MediaWiki 1.18, we had a really beautiful page that had a good, easy to read, easy to scan, summary of the things in 1.18. I'm not sure we can make this page as nice as that, but I would like something a little better than what we have right now. Today, I'll be working on updating the page and I invite others to join me.
Topic on Talk:MediaWiki 1.19
I contributed some important details to the MediaWiki 1.18 page, and I'd be happy to jump in with this one as soon as I feel competent. Thanks for making me aware of the need.
Also have a look at MediaWiki 1.19 which we'll be rolling out next week.