This change, while necessary and probably inevitable, is a huge loss for WordPress 3.6. Sadly, it seems that most people won't really understand why. To wit:
@Rob Lawrence -
But why would you use a separate post format? I don’t get it. It’s all posts.

Most likely with a video or audio file you would have an intro bit of text and other elements on the post anyway other than just the separate post item. You can embed all those things INTO a post.

I still don’t get why you need a separate post type. Please explain. Why would this be useful?

I think this is a fundamental misunderstanding of what Post Formats are - and that's quite sad, because Post Formats are an incredibly rich yet severely under-utilized feature, due to that misunderstanding. Here's something I wrote - two and a half years ago - detailing just a few of the possibilities with Post Formats, even without the now-removed UI in WordPress 3.6.

The fundamental misunderstanding of Post Formats is that they are not a post type, but rather a taxonomy. Where as the category and post-tag taxonomies describe the nature of post content, the post format taxonomy describes the format/medium of post content.

The inherent problem with the original implementation is that it was meant primarily as a taxonomy, rather than as a schema to define standard content for each format type; thus, the underlying API code introduced with the WordPress 3.6 post formats UI improvements would have opened the door to something quite significant: true interoperability and portability among all Themes that support post formats.

That portability/interoperability is one of the main reasons - if not the main reason - that post formats were first introduced. Prior to post formats, creating a gallery archive required users to create an arbitrary term, as defined by a given Theme, for the category taxonomy. One Theme may require users to create a "gallery" category, while another Theme may require some different term. (See also: "audio" vs "podcast" vs "mp3", etc.) But with post formats, Themes simply developed around the standard post format term, "gallery", or "audio", etc.

Or another possibility: synchronizing status updates with social network sites. A Plugin developer could easily create a Plugin to push/pull, for example, Tweets - but without the "status" post format type, the Plugin developer would have to use some arbitrary way to determine which posts to push/pull (e.g. via a "tweet" or "twitter" or "status", etc. category).

There are so many ideas that implement post formats in interesting and innovative ways.