After looking at the pile of "marked as new" articles I have in Bloglines, I realized most aggregators are pretty poor at helping me forage, pull the meaty bits out of, the information they collect. Adding tagging is a start, but get the dang things out of my, at least that's the problem with Bloglines. Don't get me started on the laboriousness of "clips" in Bloglines.
NetNewsWire is a bit nicer in that it'll pile marked articles in a special folder, but it's still only one pile. And while I know I can drive NetNewsWire through AppleScript to act on items in that pile, action in aggregators is still a second class citizen.