Windows Phone 7 will be available in time for the Holiday Season, Microsoft says, and today the company unveiled a beautiful new RSS reading app built by an award winning team of Microsoft 2010 interns.

Called Headliner, the app adheres to the design standards of the rest of the OS (delightfully attractive, for Microsoft) and includes most of the features that mobile RSS users will want. See the demo video below and marvel at the slick UI, the clean display of feed items and the social media integration. Then tell us what you think it’s still missing. I can only think of one or two things, really.

It’s got a River of News view (most recent articles from all subscriptions), Google Reader sync, share via Twitter (some Facebook action would be nice), recommended feeds, a mysterious feature called “reset subscriptions.”

What’s missing? Instapaper or ReadItLater integration would be nice. Personalized feed recommendations, too.

More than anything else, though? A mobile feed reader needs a quality sorting system. Google Reader has Sort By Magic, you can use the Postrank browser extension on the desktop and my new favorite mobile solution is My6Sense. When you’re on the go, you want the option of seeing just the most high-quality stuff. Scanning and pecking works great when reading feeds on the desktop, you can process a full river of news no problem that way, but mobile needs to bring you the best content from your subscriptions on a platter.

That said, Headliner looks pretty nice to me. I hope Microsoft bundles it with the OS so that millions more people can be exposed to a quality feed reading experience.