I bought NetNewsWire a while back. I'd been putting it off for years, saying I wasn't going to buy it until it could synchronize between my PowerBook and PowerMac. (Ideally, I'd like a Linux version too, and to be able to synchronize with that.)
So they got me on a technicality. NetNewsWire 2.0 has synchronzation. Two kinds, in fact. But I can't use either. One kind is Rendezvous (sorry, but "Bonjour" is just too stupid a name; even ZeroConf is better than "Bonjour"). The other kind is FTP. Yeah, FTP. Unless I've accidentally slipped back in time to 1995, that's a pretty weird choice. And I'm not making it up, either: here's proof.
Who has a server they can log in to in plaintext, and upload files to? And who wants to use it, even if they do? Presumably Cocoa has great support for ftp: URLs that made it more convenient than scp(1). (I tried and failed to write a GUI ssh-askpass for Mac OS. I followed the instructions in the man page, but I just couldn't get my program to be called. I'd imagine that was the stumbling block.)
What else don't I like? Well, there's a nasty parochial US date format, for one thing, blithely ignoring my configured ISO date format.
And it's a bit slow on my 2001-vintage PowerBook 666 MHz, but that's a slow machine anyway, and I'm just hoping it will hold out until the first round of Intel-based laptops arrive.
What's good? In brief, "everything else".
If you're stuck using, say, SharpReader on MS Windows, you have no idea how good NetNewsWire is. Perhaps not good enough on its own to justify getting a Mac, but almost. (If you're a Mac user, you have no idea how bad SharpReader is. Though I'm sure it seems fine if you've never used a decent RSS reader.)
I really like the disclosure triangle view, which you don't get in the free NetNewsWire Lite. Being able to open posts in tabs in NetNewsWire is more convenient than opening new browser windows, too, though ideally I'd like to have the WebView instances embedded in the disclosure triangle view, rather than on their own tabs. For some reason I never remember to close the tabs until I've got too many. I tend to go "back" by clicking on the next feed.
The HTML differencing is great, too. You know how it is when someone updates a good post, and you care about what's changed, but they haven't clearly marked the changes? You can pretty much forget about that. NetNewsWire will show removed text like this, and show added text like this. Simple but effective. (It uses this script, which can be fooled, but seems to work pretty well most of the time.)
I really hope the next version of NetNewsWire gives me scp(1)-based synchronization, or something equally convenient and yet secure on the public internet, but other than that, I'm pretty happy. Everything else is good enough that, especially considering that I could be stuck with RSSOwl or SharpReader instead, it seems almost churlish to complain.
[A couple of people have suggested rsync over ssh, or stunnel and FTP, but that's not convenient or fool-proof enough for me. The rsync solution in particular, because it requires me to be responsible for only running NetNewsWire on one machine at a time, and not running it while I'm doing the rsync. This should be NetNewsWire's responsibility.]