There isn't all that much hard data out there.
Mac-USB3 has some relevant info, even though it's not exactly frequently updated. AFAIK, Snow Leopard has USB-3 support built in, but that doesn't do you (as PPC user) any good. That means you'll need some other source for drivers, presumably the hardware manufacturer/vendor.
As to when prices will come down, that'll likely be a function of the bus' adoption rate, which is not supposed to pick up much before 2011. Still, this may not be a major issue, depending on the initial pricing relative to that of similar hardware for other competitive buses.
