I'm with venomz; it's going to be at least a year before we start seeing widely available Thunderbolt peripherals, and even then I'd expect them to have the same kind of price premium currently found on FW800 peripherals versus simple USB2 ones. I could be wrong, but given that USB3 already has a pretty decent foothold for such a new technology, and it's easy to add to a PC (which is what drives the price of universal peripherals), I'm willing to bet that USB3 remains cheaper for the foreseeable future.
It's also worth noting that unless the SATA-USB3 bridge is poor, the real-world sustained transfer rates from a single modern hard drive are nowhere near what either USB3 or Thunderbolt can sustain. So even if Thunderbolt drive docks/cases were readily available, the still wouldn't be much, if any, faster than one connected with USB3 in real-world situations. If there's a price premium on the Thunderbolt drive, there's a legit reason to want a USB3 one.
Not saying Thunderbolt is a bad technology--I'm quite excited about it, in fact--but there's a very obvious reason for wanting USB3 ports on a Mac sooner rather than later--I currently need to buy FW800 cases for my mini home theater/server, and even those are a bottleneck. If I were able to instead buy a cheap USB3 drive case, I'd be quite happy with that.
I'm actually considering buying one of those CalDigit cards for my new MBP, so I'll have that as an option, and I'm also going to get an eSATA expresscard, so I can get faster transfers from my external drives NOW rather than waiting until I can afford Thunderbolt drive docks.
Also: I'm pretty sure the reason Apple isn't shipping anything with a USB3 port yet, and may not for a while, is because they're using Intel's chipset, which doesn't support USB3. They'd need to source a USB3 controller from another vendor and add it to the motherboard or a mini-PCIe card, which I can kind of see why they would want to avoid on the MBP line.
