I also have the opportunity to play on a U1 I Yam.
Note that I played on this instrument in the conservatory
in a room for the flute or piano accompaniment serve a
and repeat students. It is therefore very busy, and I think it deserves a review. So I put my opinion on the subject:

On the positive side
It is quite a hit
-Mute
Right-to-finish

for negative
-The bass is horrible (10 bass notes first wholesale)
-The highs are not very pretty either (like a lot of Yamaha)
I think the overall sound is very muffled.

voila, but again, I have not played a new piano.
Friendly