Back in the day I was a Usenet fiend, but I'd fallen away until very recently; I returned courtesy of NewsgroupDirect, a good, Mac-friendly third-party Usenet provider that provided a review account for TUAW use (you generally have to subscribe these days for Usenet access). What I was surprised to discover on my return was the advent of NZB files and search engines which make it extremely easy to find binaries (unlike the old days when you had to look for everything manually). The new version of Unison offers native support for NZB searching within the application (via binsearch.info and others). It also automatically takes care of finding missing parts, PAR recovery, and RAR unpacking. In short, Unison is now clearly your best bet on the Mac for Usenet binaries.
Of course Unison also retains its older message reading features and adds handy new ones like threading. There's an updated interface and the general level of Mac goodness one associates with Panic. Unison 2.0 is $29 ($18 upgrade from version 1) and a 7-day demo is available. If you need a Usenet subscription, Panic is offering the companion service Unison Access for $9 a month; NewsgroupDirect offers a range of plans from $8 to $20 per month.