In my opinion, this app is the slickest, cleverest, prettiest and best designed RSS aggregator out there.
The feature set of NewsFire is impressive, and once learned, allows for very quick and intuitive management of large amounts of feeds. The ability to create folders and smart feeds is nothing the others can't do, but seems more elegently implemented somehow. Feeds can be hidden too, which, combined with an intuitive smart feed system makes for a great way of getting just the info you want and not all the clutter.
Just about every aspect of the app is customisable via preferences. The author really has thought of everything.
All this is displayed in the most beautifull crafted interface possible on Mac OSX. Davis Watanabe is something of a genius in this field. The man bleeds cocoa. The interface is simple and slick, and makes nice use of quartz effects. Being a GUI junkie, and exclusively using ShapeShifter themes, I have to say that no other app has ever so seemlessly just "worked" without any need for specific theme elements. This is the mark of a truly modern and elegant GUI.
However, I agree it is a little too expensive. I used it for many months when it was in Beta, (and free). Once it became shareware, I spent a long time trying out all the alternatives, and while almost all are cheaper, they all came up short in one way or another. I would think a price of $9.99 - $12.99 is more realistic given that apps such as Vienna are very very similar, and are FREE. $18.99 is a little too high (although I paid it).
As for the author not replying emails, well, I have never had reason to email him. My registration was completed in seconds, and I have had no issues with the app. I have only seen it crash twice and I use it continuously.