I think the piano sounds are okay. Would I want to use it to make a high-quality recording, I don't know. But for practising it is awesome. I also use it in my piano-teaching studio.
I would like to see Casio come up with a midi pedal-keyboard (like 2octaves) that you could connect to the keyboard and use it for practicing church-organ stuff. Viscount makes such a thing, so does Roland; theirs are pretty expensive though.