I had a C750 which I sold off. As far as I know - all the three previous models - the C750, C760, C860 had the same keyboard.
The C1000 keyboard is definitely better than the C860 (or C750 as I know directly).
The C860 keyboards were film based in that the keys were attached to a film kind of base and so when you pressed on eky, the area around it would also deoress slightly (not to much that another key got pressed).
But the C1000 keyboard is more solid and each key raises up from this solid base, so it also feels more tactile.
But typing speed wise - i dont think it makes any difference, since the layout is nearly the same.