I started researching free RSS readers several months ago after finding it to be too time consuming visiting such a large list of bookmarks in Firefox. Sure, Firefox has Live Bookmarks, but have you used them? I personally think they suck a bit. So, the RSS reader search began. I found quite a few commercial apps but I really didn't want to pay anything for something that is essentially an XML parser/aggregator.
After trying about a half dozen, I stuck with Pulp Fiction Lite for about 4-6 months--hard to say just how long without looking at timestamps on the files. It is a good, slightly crippled version of their commercial product. Unfortunately, even though it was the best of those I tested, I wasn't in love with it.
Recently, I came across Vienna which is a free, Open Source RSS reader for Mac OS X. With the exception of Microsoft Office, I prefer running Open Source software. Vienna has been quit functional and more user friendly than Pulp Fiction Lite. It does seem to be a little more picky about the RSS feed being fully compliant with RSS standards as a couple of my feeds have been reported as bad. Going back to the source of the feed, I was able to try one of the other versions (RSS .9, 1.0, 2.0, ATOM, etc) and got past the problem. To help solve the problems with the feeds, it has an option to Validate Feed, which sends the feed to the Feed Validator website.
Vienna has quite a few features that I haven't even delved into yet but I expect to get around to them. They include Groups, Smart Folders and Custom Styles. A very cool app, indeed. If you like freeware, Open Source apps and need a solid RSS reader, check it Vienna.