I've used Safari to read feeds for a long time, but after a while it makes Safari terribly slow, suddenly a page load takes at least 5 seconds. Cleaning the feed cache makes it fast again, but it doesn't take long before it starts slowing down to the old crawl.
I got fed up with it and invested $31.19 (including the 25% Danish sales tax) in NetNewsWire and I'm really happy with it. NetNewsWire is a better and faster interface than Safari, and having removed all the bookmarked feeds from Safari it's suddenly back to it's old snappy and fast self.
I also tried NewsFire, “Mac RSS with style” as they call it. It does look pretty, but I don't like its interface. As far as the other feed readers I found goes, none of them looked intereting enough to give them a try.