This was announced on the Internet Explorer Blog today! So this is both good and bad. It's good because the adoption of IE7 will be much faster than if it was left to users to download proactively. It's bad because us web developers will now have to support IE7, as well as IE6, Firefox, Mozilla, Opera, etc. It's just one more browser to think about.
Of course, it SHOULD be more standards compliant, and therefore more cross browser friendly. Let's hope for a solid launch!