To import an OPML file into IE7, press Alt. The menu appears. Now select File/Import and Export. The Import/Export wizard appears. Press Next. Select Import Feeds. Press Next. Browse to your OPML file. Press Next.
You will then have all your feeds in the favorites center in the Feeds tab. While the presentation of a single feed is very well done, it does not really scale to support a big number of feeds.
First, if you sort your feeds into folders, there does not seem to be a way to display all news items aggregated over a folder. Second, while you can set properties for an individual feed, you don't seem to be able to change settings for all feeds in a folder at once. For example, the default update interval for a feed in IE7 is once a day. You can change this for one feed by right clicking on the feed in favorites center, select Properties from the menu, and adjusting refresh frequency. Now I want all my feeds to update every 15 minutes, and I have got 60 feeds or so. The only way to do this seems to be to update the properties for each individual feed.
If anybody knows how to work around this, please let me know.