NNW is very simple to use, you can start using in a matter of minutes. But as simple as it looks it's full of surprises. Among what I prefer, it tells you how many new entries have been gathered that you haven't read yet (even lists them in the Dock), it stores the feeds for offline reading (very handy if you plan to catch up offline) and the weblog editor is a relief compared to filling forms in a web browser.
It's a 1.0 version so don't expect it to be perfect or bug free, but it can only get better. The developer -- Brent Simmons -- has been very responsive to requests during the beta testing. I'm looking forward to the integration of Apple's WebCore (from KHTML, the engine behind Safari) which should make the rendering just great.