My feelings, based on playing a very large number of pianos from most of the makes found in Europe:
Yamaha builds a piano down to a price. I have no time at all for the company's smallest grands, which have a nasty, metallic sound and out-of-tune bass strings (that's bad string quality, not a function of how they have been tuned by the last technician to tune the piano). The medium-size ones, and the uprights, are just about serviceable but they seem to wear out fast and I don't often find them very interesting to play - they are very much factory instruments. The very top models (basically the CF concert grand and one or two models just below that) can be very good but don't seem to bear much resemblance to most of the rest. I really can't find much to like about most Yamaha pianos and I prefer Kawai and, in some cases, some of the better Chinese pianos. I certainly prefer many of the European makes. Can't comment on USA-built pianos because they don't turn up in Europe much.
Keyboards: I find the Yamaha ones seem to develop an annoying level of mechanical rattle quicker than similar models from Roland.