Thunderbolt is like the early days of FireWire, IMHO. Expensive, and NOT, N. O. T. not an intended replacement for USB. Simply, it's an expensive but very high speed I/O. People singing it's overture are forgetting the FireWire was around for YEARS before it became standard on the Mac and was VERY VERY expensive initially.
That said, I use it for my Cinema display (so, in miniDP mode) but nothing yet. For my uses, a cheaper USB 3.0 drive is adequate. Honestly, I'd like to see some real world numbers. USB 3.0 @ 5Gbps seems, to me, plenty fast enough for a spinning hard disk. It is, in theory, 5/6th the speed of SATA III. Now an array of SSD's is another story, but, I am curious if a spinning hard drive is actually faster via thunderbolt or not.
Also, OP, I've heard that some folks are supposed to be coming out with a thunderbolt to USB 3.0 adapter (And there are already USB 3.0 'docking stations'). But, for the price, WHATEVER it is, I'd think a USB 3.0 hub would work just as well. Even though I don't use it, I wouldn't trade it for another USB port. It isn't an 'extra' port as it's the existing miniDP port that's always been there, and I don't want to get rid of my external video support. I use it every day. And who knows, one day I might use it, especially if docking station prices drop.