I'll second the nomination for Unison. I'm a recent switcher and was a heavy XNews user for years and years. My first priority was to find a good Usenet reader for OSX, and I tested them all: Thoth, Thunderbird, MTNW, Unison, you name it.
Unison has an absolutely beautiful interface, and the way it groups music files and images is second-to-none. HOWEVER, it is seriously limited in flexibility and advanced functionality if that's what you're after, but I'm keeping my fingers crossed that the lads at Panic will continue adding more of the sophisticated features in the near future.
Due to your dislike of Thoth, here's another vote for Unison, and a hint about Hogwasher (which costs money and has a learning curve). Hogwasher is another powerful Usenet reader, that many swear is without equal.
Otherwise, I must say, Thoth is a very competent Usenet program. It may be discontinued, but it's a full featured Usenet reader that will be missed. I use it constantly.
I tried it some time ago, but have stuck with Hogwasher, which I've used for years and really like. Version 4 has just been released, and there's a 60-day full-feature trial period.
One of the nice new features which I believe is unique to HW is that you can set up a newsgroup to be accessed from 2 feeds - so if your primary feed isn't complete you can designate a second feed to complete it ...