I was pretty sure that there are some feeds that get found by IE7 yet don't display correctly if at all in the "Feed View". If you direct Internet Explorer 7 towards channel9.msdn.com, you should see that it detects a feed is available, now if you try and view the feed all it shows is the XML.
Why doesn't it XSLT the feed correctly. I don't know? But if you do, let me know. I am thinking of starting a list of feeds that do not appear to render correctly, it might be a bug, it might not. But if anyone from Microsoft stumbles accross this site it might help them.
If anyone who reads this blog [I know there are at least three people now :)] knows any feeds that don't render drop me an email [email@example.com