An unusual release, this. There’s just one new feature, and it’s not one that’s been necessitated by my work or by requests. I won’t do this often, but I recently noticed the Post Meta Inspector plugin, which outputs all the post meta values on post (and page, etc.) edit screens. I realized this is a very simple, but very useful feature. I know that it will save me endless flipping back and forth between WP and phpMyAdmin when I’m trying to track down a custom field issue.
It parses and dumps serialized data. There’s probably other enhancements that are possible, but for now I think it’s useful enough.
Due to the media changes in WP 3.5, as it stands it won’t output on attachment edit screens for previous versions. I don’t think I’ll bother with this—but I probably will find some time in the future to add it to user edit screens, which aren’t currently supported.
There’s no way to turn it off, but if it’s in the way you can fold the meta box up, or hide it with Screen Options.