UPDATE: I finally found the disappointing answer: All the new Studio "c" audio interfaces are only being run in USB 2.0. Why would Presonus release another USB 2.0 audio interface when there are already a thousand of them on the market? The "c" mini connector doesn't get you anything if it is only still running USB 2.0. The connection is just different. USB 3.0 would have been 10 times faster, and USB 3.1 would have been on par with Thunderbolt.
Is the new Studio 68c running on USB 2.0, 3.0, or 3.1? This spec makes a huge difference in performance, and it isn't spelled out anywhere.
I downloaded the Studio 68c user manual, and it explicitly says that it is BACKWARD compatible with USB 2.0 and 3.0, which seems to mean it is running on USB 3.1. You can't be BACKWARD compatible with USB 3.0 unless you are currently 3.1. However, a lot of consumers are saying these new Studio "c" interfaces are only running on USB 2.0.
So what is the true spec, PreSonus? I would fork over money in an instant for a USB 3.1 audio interface, but another USB 2.0 interface doesn't gain me anything.