I've been playing around with Feed24 and concluded it has great potential. Essentially Feed24 is a search engine for RSS feeds only. The results come back with a link to the source RSS feed, a snippet of the article, date posted, a link to a 'parasited' page of the source (but not the orginal posting). At the time of writing, Feed24 carries 256,401 feeds with 5,615,246 messages are fully searchable by Feed24.
One significant criticism I'd have is the weakness of its search algorithm. As an example, if I search for 'think week', it comes back with results that include the word 'think' or 'week', but buried (miles away) away is the first result with both words in the order of the query 'think week' (even if the 'by relevance' bit is toggled)....today, there is no Advanced Search to even force the function. Search 'Bill Gates Think Week', and the results get close to what I'm looking for.
What is very nice is the ability to subscribe to a search results RSS feed, so as new posts are published wthin the feeds it tracks, you can keep track.
If the team can work on the search weakness, I'd say Feed24 has the potential to be extremely useful.