I received the following official feedback from Microsoft about my concerns regarding RSS support in IE7:
This is not a bug. This capability is not offered in IE7. The support for feeds in IE7 is meant to be relatively basic and to work with the new RSS platform. Writing a fully featured RSS aggregator is not going to be part of the IE7 release. This will be considered for future versions but IE7 will not ship with this feature.
Others are also going to use the RSS Platform to build more fully featured RSS readers in addition to the basic support in IE.
Now that actually makes sense now. Instead of exporting and importing feeds via OPML files, the feeds will be stored by the platform, and the aggregators can be build on top of that. Then you will be able to use not one but several aggregators, and if you subscribe to a feed in IE (or any of the aggregators) all the aggregators will display the new feed.
So you could have IE, a gadget in the sidebar that just displays the most recent items, and a full blown aggregator side by side.