I read over the SATA-IO.org white paper on SATA III and although it is not very specific, here is what they said about the cables:
"SATA 6Gb/s Cabling
The same cables and connectors used for current SATA implementations can be used to connect SATA 6Gb/s devices. SATA-IO recommends utilizing quality components to ensure data integrity and robust operation at the fast 6Gb/s transfer rate."
They don't say anything about using larger wire gauge, or if the A and B differential cabling is twisted or twisted differently, so it probably doesn't matter. They did mention that at the longer distances (up to 1 mtr) the voltage could decrease and there could be more jitter.
Logically at 9, 12, 18" which are pretty much the lengths used inside a case, there shouldn't be any problem.
Wonder if anyone else has had any positive or negative experience with the 6Gb/s cabling