transfer speed – added a new transfer type called Super Speed or SS – 5 Gb/s (electrically it is more similar to PCIe Gen2 than USB 2.0)
more bandwidth – instead of one-way communication, USB 3.0 uses two unidirectional data paths: one to receive data and the other to transmit.
So each usb 3.0 connection has what you could call 2 lanes. But physically, I think you would see only 1 lane (though I'm not certain of that).
Usually, I think that USB cards may have many ports, but only 1 lane. So let's say you have a USB 3.0 card with data transfer capabilities of 5GB/s and 5 ports. If 2 ports were in use, each would have a bandwidth of 2.5GB/s. If all 5 were used at the same time, each would have a bandwidth of 1GB/s available.
No it does not exist for "normal" consumer. There are no PCIe to USB 3.0 cards that can connect on multiple PCIe lanes. Also, as far as I've seen, these types of card are all PCIe 2.0 1x.
Maybe for businesses something custom could be made to work with a PCIe 2.0 (or 3.0 now that it has finally arrived) 16x card, which would have a lot more bandwidth available. After a 10 minutes search on that subject on Google, I found nothing.
(HighPoint Second Generation Quad PCI-Express 2.0 x4 HBA USB 3.0 Port RocketU 1144B).
You're paying a lot for it.
Which uses a x4 pci-e link and has 4 ports. Need to factor how much bandwidth you'll actually be using though. If you have external hard drives on all ports with a raid-setup, you need it, but if you aren't going to be hitting all the ports at once, 4 ports on one x1 link isn't bad.