I like the lower and higher registers of the USA grand, however, to my ears, the attack in the middle few octaves imparts a kind of plasticky sound that has a "phasey" decay and is detached from the overall tone of the sample. It's hard to explain....The overall tone seems ramp down too suddenly before the sustain portion of the note/s, which feels unnatural. I observe this to varying extents with others including German, Italian, Japan, Aus, Blu, pop and rock as well.
Vintage, taperec, upright etc. don't exhibit this behaviour and seem more authentic and expressive to me.
Having said all that, I acknowledge that different amplification has an impact on this phenomenon. It is more apparent using headphones than with powered speakers.
Interestingly, the *equivalent* sound on the numa player has a better attack/decay character and feels more expressive than the USA grand patch on the X piano... As does the electric grand patch... Love the numa player electric grand, don't love the ones in the X piano.
The GT action is really nice and feels well made. It is very quiet - I've had a few Kawais and a Roland RD-800 and the GT is way quieter than those. The keys also have a nice texture and the build quality and feel really is premium. I don't notice any mechanical noise of the keybed when playing. Virtually no thunk at all. The keys also do not wiggle from side to side and have no key bounce as far as I can tell. Interestingly, the action seems more suited to some internal sounds than others in terms of "connection". For some reason it's easier to play faster, more complex pieces with some samples than others (notwithstanding my mediocre abilities).
I also really liked the feel of the tp110 action when I tried it. I feel like it was a bit lighter, very expressive and suited to the EP's especially. I was all set to get the non GT version but sprung for the GT because I felt like the action needed to be an "upgrade" from the Roland. Ridiculous, I know... could have saved a lot of money and my back and still been very happy, I'm sure. The GT is heavy!