I used NetNewsWire Lite a while back (the last time I used Firefox), then I switched to Safari 2 (which has awesome RSS handling), but when I switched back to Firefox (when 1.5 came out) I was recommended Vienna, gave it a try and never looked back...
Newsfire RSS, NetNewsWire and Endo are all really good. In the end, it comes down to what works best for you. There is no best RSS client for everyone. Right now, I prefer Endo.
Mac users really have an embarrassment of riches in this area. Other programs not already mentioned include NewsMac, PulpFiction Lite, and RSSOwl all of which are free. I started out with NetNewsWire Lite (also free), but upgraded to the full version because I like having the built-in browser.
Vienna also has a built-in browser... and it's free... and very "Mac-like", for those preferring that...
I don't use it, I prefer to open the links in an external browser, i.e. Firefox, but you could only use Vienna, if you want to (I even think that's the default).