IMO, EyeTV is a poor software platform. Elgato has effectively abandoned it; they just haven't announced the fact!
You can get dual-tuner versions of the HDHomerun that work quite well with North American broadcast HDTV.
Both of these statements are true.
wondering why the market seems to have suddenly dried up, and hesitant to invest in a technology that may be past its prime... Anyone know of a product compatible with Mac / OSX that is still viable and easily available?
Whatever market there was for El Gato with EyeTV dried up because 1) most people don't record ATSC, they don't even know what it is and 2) cablecos have steadily and progressively cracked down on the channels they passed along in the clear, which is what most of us here were recording. But, if all the OP wants to record is ATSC in OS X on his Mac and not deal with either Myth or Windows and he doesn't care about CableCARD or premium channels, he can still do what he wants very easily and relatively cheaply--the older HD Homerun dual ATSC tuners are abundant and can easily be had for relatively little on eBay because everyone wants the CableCARD versions. Shop around for a cheap used EyeTV tuner that includes the software...which works with the Silicon Dust HD Homerun tuners...and you're all set, if you shop well probably for less than $100 total, that's one HD Homerun dual tuner, one cheap El Gato USB stick tuner, the EyeTV software plus a year of TV Guide. If you're satisfied with network shows this still is a viable way to cut the cord...keep your internet access though so you can still supplement with streaming and downloading.
I'm fine going with a used model, but...hesitant to invest in a technology that may be past its prime
Don't be hesitant, you just want to record ATSC, you should be able to do that quite well for some time, certainly enough time to earn back your $100 investment many times over.