Don't get me wrong, I am one of the innumerable converts who have taken to reading news and blogs via newsreaders instead of jumping from URL to URL. Navigation is uniform across all site-feeds and the convenience is too much to be ignored.
But after using some of the best newsreaders (both desktop and web-based), I've come to realize there's at least one critical flaw that's innate to all of them: the lack of hierarchy in news presentation. All news items get the same amount of coverage irrespective of how vital or trivial the issue might be. So India launching a foreign satellite for the first time is only as important as an unknown girl eloping with an equally unknown boy when viewed through a newsreader!
The other flaw, those less critical, is the problem of redundancy. When you read news from multiple sources, you often come across the same issue being covered by more than one. Although the same problem persists if you prefer URL-hopping, a better alternative is to stick to one site that covers it all. And if you indeed rely on a particular site for most of your news cravings, a newsreader would make little sense except for subscribing to the lesser or more specialized sites and blogs.
Here's my pattern. I rely heavily on Yahoo! News (the most trafficked news site on the Net). The labor pains are too much for me to individually visit the other news sites (mostly science, technology and editorial) and blogs. So I read them through Google Reader or My Yahoo. These two readers have vastly different approaches to newsreading and I guess the perfect reader would have to a hybrid of the two, disparate though their approaches may seem!