Microsoft's RSS team blog has this news.

"IE7 Beta 3 is here! We’ve snuck in some goodies in the feed reading user experience based on your Beta 2 feedback"

The post provides details on the new RSS-related features.  More feedback sought.

If you have previous IE 7 Betas installed you need to know this (from the IE7 FAQs)

"Upgrading Internet Explorer 7 Beta 3
If you want to reinstall Internet Explorer 7 Beta 3 (or install a newer version) you must first remove any existing Internet Explorer 7 beta versions on your system. You cannot install Internet Explorer 7 Beta 3 over previously installed Internet Explorer 7 betas. To uninstall previous versions of Internet Explorer 7 refer to the uninstall directions below."

The IE team blog has more on this.

Update:

 Max Stevens, Lead PM on the IE team shows some of the UX improvements made for this release.