I used NetNewsWire back in the early '00s, but it has become a complicated beast, and after learning about Reeder beta 1 a few months ago, I was an instant convert.
Reeder is great, because all I ever do is arrow-down through news stories, glance over ones I might be interested, press 'B' to open the really interesting articles in my browser, and then press 'A' then 'return' to mark all stories as read.
It's fast, simple, elegant, and hides a ton of extra complexity (in case you want to do more with it than I do). I love it even more on the iPad... it's simply the best solution for iPad or Mac. I don't bother reading news feeds on the iPhone much, though (I use both NetNewsWire and Reeder on that platform).