Shrook 2 is a next-generation news reader that offers advanced features not available to Mac users anywhere else. Some aren't available on any platform. It supports all versions of RSS, as well as the current draft of Atom. And it's all really easy to use, too. Shrook 2 is a free upgrade for users of Shrook v1.x.
[ I'm sorry to hear that it's a bit unreliable... I've been looking at installing an aggregator on my mac, but didn't want to pay for NNW. This thing appears to have some really nice features, like being able to check your feeds online or from multiple systems, and have all your instances sync up... very cool. Also, the mirroring of feeds to mitigate publisher loads is a good call. I look forward to version 2.1 -k]
Shrook 2 - RSS and Atom Newsreader for Mac OS X