Take a look at this Intel developer's blog:
The video shows a USB flash drive transfering video at 125MB/s! To give you an idea of this speed, it is likely more than your hard disk can put out which is probably around 80MB/s. The rest of the article gives a good overview of USB 3.0 and she states that the bus should have about 400MB/s bandwidth in the real world. This is a breath of fresh air for external devices of all sorts, and I can't wait to see this on new computers.
The Linux drivers are currently under development, with the subsystem patches going into review. xHCI driver will have to wait until Intel finalizes and releases the specs. Anyways, it's safe to say that Linux should have USB 3.0 support as soon as products hit the market in the middle of 2009.