I haven't read anything about this so far and so I thought I might share this with you:
USB3.0 controller card based on NEC D720200 is working out of the box in my N40L. No driver installation required! ~100 MB/s without any issues. I tried this card as my DS1812+ also uses that chip for USB3.0.
Only drawback seems to be missing hybernation, probably because DSM is installed on USB stick and DSM activity seems to prevent hybernation for all USB devices.