RSS Bandit seems kind of sparse. There's a new UI in the works, but I couldn't get to the screenies, because of bandwidth quotas. You can adjust polling frequency of different feeds, which is really nice. There is support for Comment API, but I couldn't get this to work. Source code included but licensing is unclear. At least there's the chance to help / fix stuff.

SharpReader - I like the filtering and UI for changing refreshes. There doesn't appear to be per feed polling. The threading feature is really nice, but constrained by the tree/feed oriented UI. A "thread" based UI/display would be great here. Clicking a folder/category displays the titles of all the items in the folder, which is closer to what I want. Locking an item is good -- being able to put it in a virtual folder (like to-do folder) would be better. I like that you can specify the number of concurrent connections. Unfortunately, I also experienced some annoying delays.

Harvester - I like the UI, sort of. There's no indication of whether items have been read or not. The tabbing is nice, but it doesn't work the way I expected. I get a new tab no matter what. I use Mozilla tabs and Aggie to form a "placeholder" system of things that I want to come back to. Aggie puts all the items into one BIG HTML document, ordered by feed. I just scroll through the document (skimming mostly) and middle clicking (open in new tab) on items that need more time or a post/comment/respose. Harvester's way of creating a tab for every item doesn't help create that working list. A the moment there's no per feed polling interval. I got a bunch of exception throws in Harvester, but no crash. But for a first release, respectable. There's not much I can do to help without source. The use of the Magic library is also cool Gonna hafta look at that.

Richard Caetano describes the next step for RSS aggregators.

Most readers use a tree as a focus point. I think this works well in the typical programmer's mind but it adds little value to the information being display. What I'm envisioning is a newspaper. I would love to open up my aggregator and the first thing I see is a newspaper like front page customized by me. I might have 3 or 4 sections: .NET, Programming, News, Life. One the front page I would have blurps from different RSS sources with links to the full post. The page would represent today's news and I would be able to check the progress of my page in real time (people post at different times).

With that in mind, I would like to see the aggregator archive each day's news in a way where I could flip back through time. I may not remember who posted something but I could remember when. All this information should be neatly stored on my hard drive.