First, I have to say that practicing on a grand is absolutely necessary to develop a good technique. I find any and all uprights simply too light to the touch, so when you get to a grand during performance, your fingers have to fight and gasp for air!
Secondly, Shigeru vs. Yamaha? Shigeru wins hands down. period. Yamaha is machine made. Shigeru takes a year to painstakingly be made by hand by craftsmen that make pianos for a living. I am even going to say that the Shigeru, in terms of quality, is better than almost all pianos made in the U.S, since based on observation, Japanese craftsmen put more time, effort, and passion into the creation of a piano. (Japanese people have been known to commit suicide when getting fired from their jobs).
In terms of sound, I briefly touched and played a shigeru, and have to say that the sound was magnificent. The only downside is that it costs almost as much as a well known brand like steinway or mason and hamlin, while it lacks the name recognition of the big boys, so in terms of resale it isn't good. I can confidently say that the Shigeru Kawai will definitely gain the recognition it deserves in the coming years. Definitely.
Another downside is that the parts are all japanese, and i don't know the quality or performance of these japanese parts. I'm sure they need more experience in making their own parts, as oposed to steinway, which either uses its time tested and artist approved action, or the universal rener action.
Overall rating: great for personal use, if you don't plan on selling it.