It would be very nice to be able to use the RSS Feed Builder to become more of a general Notification Feed Builder - which would define the content of the feed (abstracting it from the output mechanism). This would enable the addition of various outputs, the following 3 I think are most desirable:
1. RSS XML (already existing)
2. HTML - The above, when viewed in a browser, should look similar to search results (or possibly blog results showing multiple blogs)
3. Email Notification - Through "watching" the feed - linked from the feed main page, and from the html above.
This would allow the user to choose how s/he gets their notifications as everyone has their own preference, and far more people have an email reader than an rss reader.