The good news: I upgraded to 5.5 and now my USB 3.0 adapter works. I connected it to my Win7 x64 VM and so far it's functioning as expected.

My adapter is a NEC based chipset marketed as the StarTech 2 Port PCI Express SuperSpeed USB 3.0 Card Adapter Model PEXUSB3S2

The bad news: I am a home user and have uncovered an unfortunate issue with the free version of ESXi 5.5. vSphere Client no longer supports editing VM settings of a version 10 machine. You must use vSphere Web Client which requires vCenter. I downloaded a trial copy of vCenter Appliance and vSphere Enterprise Plus so that I could make the required pass-thru edit from vSphere Web Client.

I'm not sure how I'm going to administrate my host after my eval licenses expire.. : (