The answer partly depends on what kind of newsreader you want, and whether you're willing to pay for it. It sounds like Newsbin Pro is a paid, binaries-centric Newsreader, in which case, I'd check out Thoth.
http://www.thothsw.com/thoth/
I worship Thoth since I'm seriously into binaries groups--it's good enough that I gladly paid the $25 shareware fee, which is exceedingly rare for me.
For binaries groups, Thoth can handle tens of thousands of individual messages at a time, has essentially perfect auto-grouping of multipart binaries (I have yet to see it make a mistake), automatically decodes uuenc, mime, and yenc binaries, allows the queuing of literally thousands of downloads from multiple servers targeted at multiple local folders, and you can arrange the order the whole mess will download on the fly. Plus, it's extremely stable now, with probably less than one crash per month in my use, and it's updated frequently. I doubt there are any better Mac Newsreaders for binary group fans.
It may not be the top choice for threaded message reading, though, and it isn't free. I used to use MT-NewsWatcher, which is free and still occasionally updated:
http://www.smfr.org/mtnw/
It is still, so far as I gather, a decent free newsreader, but it's not the best for binaries.
There are a lot of others, but I haven't used any so I can't offer any advice. If you haven't arleady poked around on VersionTracker.com, I'd have a look-see.
