Hi, Roger
The definition of "nice" has given me a little trouble in the past. My dad taught physics. To a scientist or a mathematician, "nice" applied to a proof or a piece of work is high praise.
But when I was in a conservatory, and told someone that a performance was "nice", she was offended. To her mind, "nice" applied to a musical performance implied that it was trivial.
As for a Matthushek square (I looked after one for a few years), if in good original condition or well rebuilt, "nice" suggests that it is pleasing in a quirky way, which is a quite accurate description of this unique model -- a square way after the time of square grands, not a grand, not a spinet, so they called it a spinet grand, all kinds of work-arounds to accommodate a very strange geometry, and yet the thing actually plays. With the narrow string spacing and the odd tuning pin layout, I found it hard to mute and it took constant attention to be on the right tuning pin -- but heck, it was a fun experience.