One thing about tape echo units...the big tape cassettes that were used on the original echoplexes made a lot of mechanical noise you could hear in the room, and to a degree, still make noise you can hear in the room (the Fulltones use a re-creation of the old tape cassette the originals used, with 1/4 inch tape like the originals, too, though it's much higher quality tape since tape improved a lot right through the 90s, hence the machines don't shed a lot of oxide, etc.). Mechanical noise in these types of machines has always been something of a drawback, even though the good ones sound marvelous and of course, the noise in the room doesn't show up on recordings unless you happen to accidentally mic the echoplex with a room mic, which of course I have done!). In any case, it'll be interesting to see how noisy and how reliable the transport on the T-Rex unit will be.
What's interesting is that the big tape recorders of the 70s-80s era, with high end motors and transports, were dead quiet in a room, unless a tape reel had a bent flange that scraped against the tape and caused a warble (hence the term "flanging"). The open-reel machines I had until 2000 or so were
incredibly well-crafted, and I bet are still running today somewhere if anyone kept them up. We are talking big machines that were the size of a washing machine, with discrete components, and beautiful mechanical parts, that were literally dead silent in operation.
As an old "tape man," I really miss those machines. With a hot roll of tape on them, the room would get this great smell, too! And I'm pretty sure you can hear the smell on those old records, right?
The 70s were kind of an odd time for American industry, and I think that was true of all segments of the market. The first oil crisis starting around '73 or so had a huge effect on all manufacturers, whose pricing structures were clobbered by inflation and the first overseas competition. I remember that at the start of the decade, I bought a new, loaded Firebird Formula for around 3 grand. By the end of the decade, the same car was about double to triple the price, and wasn't nearly as nice. I switched to European cars, and so did a lot of other folks (or other imports).
Musical instrument makers had similar issues - my '67 Fender Bassman was bought new for maybe $250-300. A decade later the same amp was double to triple the price, and a lot of folks were priced out of the market, so they just made the dang things more cheaply. Apply something similar to a whole industry, and it's no wonder that a lot of folks find stuff from that era far from "classic."
However, there is also gear from that era that people absolutely love. So I guess there just aren't any real conclusions to be drawn. And music gear is such a personal thing! But I do love tape echo.