Blogger Shawn Blanc has written an exhaustively thorough review of NewNewsWire (We interviewed Brent Simmons, author of NetNewsWire, over the summer). He begins with a description of how he first became aware of the application and goes on to describe a history of the UI, his "favorite things" about NNW and concludes with an exploration of the paid version.
Note that Shawn intends to give other popular applications, like Coda, SuperDuper! and Transmit, the same treatment. We can't wait.