In a first for Apple iPads, the Lighting Port on the new iPad Pro supports the faster USB 3.0 -- but still somewhat old -- standard. That means you'll see data transfer speeds double and possibly additional accessories in the future.
MacRumors noted the hardware change based on iFixit's teardown of the big tablet: Inside is a Fresco Logic 4-port USB 3.0 Host Controller. Indeed, CNET's review mentioned the USB 3.0 support in passing as well.
Since USB 3.0 uses two-way communication - one for sending and for receiving - it's much faster than the single pipeline used in the older USB 2.0 spec. That one tops out around 480 Mbps while USB 3.0 can push data at up to 5 Gbps. Those are theoretical maximum throughputs that will vary on other conditions, however.
USB 3.0 can also supply more power to devices as well, which has me wondering if the iPad Pro will support additional accessories. That will also depend on iOS and apps though: I can plug in and use a USB condenser microphone to an iPad today and while it works for GarageBand, it's not supported in Skype, for example: There's no option in app to choose a mic (or a camera, for that matter).
Of course, there's a downside to this as well. Apple's current Lighting to USB cables and adapters are USB 2.0, so to take full advantage of the quicker throughput for USB 3.0, iPad Pro owners will have to buy new adapters. I suspect digital photographers won't mind picking up a new one to transfer large images from the cameras.
As for the rest of us: Well, at least the old USB 2.0 cables are backwards compatible.