Have two 478's myself, love them, bright enough to see with dark shield on and tough as nails, and I prefer buttons over touch screen.
And you are correct, there is still a HUGH market for these units, I have bought a few off craigslist, most have dead internal battery, I replace them and test the units for resale, made enough to pay for 3 sets of tires last year
In fact I have a a 276C and a 478 available now, if any one is interested.