In his review he talks about the RSS feed support in IE7 beta 1:
One of the big things talked about in Internet Explorer 7 is its support for RSS feeds. Indeed, I found a couple already in the Favorites menu. So I decided to check out the IE Blog, and this is what I got. Obviously the RSS feed support still needs a lot of work, or at least a stylesheet. Hopefully this will develop further before release, or it will be pretty useless.
In the screenshot he has on his site we see Internet Explorer displaying it’s standard pretty view of an XML file but not the nice view of the RSS we expected. I was suprised to see this as the test I had run of this feature against my sites RSS feed had worked ok as can be seen in the following screenshot.
Looking at the feed returned by the IE blog that ioerror tested with all looks well and so it seems that the detection algorithm is not quite perfected yet – you would have thought however that the IE team would have tested it against there own blog!