I actually respectfully disagree....as far as key mechanics, design, general fabrication quality, and tonality....they are a pretty common 20's horn. The pre-G#roller TT's are nothing to write home about, for example, and the NW I's and earlier, sorta the same - Matt Stohrer has done a nice video on the significant improvements which occurred between the NWI and II s far as key castings and mechanics.
The two qualities which people tend to mention most -one mentioned above already, is the slight lack of edge to the core tone and also a bit more of a flexy-ness in intonation. The former I can see, the latter has not been my impression however, they seem no more flexy in intonation than any other American model of the era, to me.
True, nobody is gonna go out and buy one, probably...but if one happens to fall into someone's lap....they aren't just wall-hangers. A little investment can actually result in a decent enough horn in the end, IMHO.