I've been hooked on Reeder for viewing my RSS feeds since the first time I laid hands on it with my iPad. I'd been searching for an elegant solution to RSS for a while and Reeder blew me out of the water with it's UI design, speed and features. So naturally I immediately bought it when it came out in the App Store.
The desktop version of the software brings everything over with it from iOS and even adds a few thing. My favourite is the way in which it displays the number of unread articles in the dock icon itself. The slightly recessed nature of the numbers, the perfect angle and perspective just show much care and effort went into making this product the best that it is.