Seems like the Mac has a huge number of RSS readers. For a while I was using Vienna, but it stopped working after a recent update (no blogs ever updated!). So I just switched to NetNewsWire. So far, I like it quite a bit!
I was even able to keep my old subscriptions by dragging them (alas, one at a time) from the Vienna window the the NNW window.
I'm sure everyone has their favorite, and its not like I did a systematic survey; just a quick couple of Google searches and decided I liked it.