USB pass-through has been part of the likes of VMware Workstation for quite some time, but is new to vSphere with the 4.1 release (July 13th 2010).
To connect a USB device to a virtual machine (VM) in vSphere you need to first add a USB Controller to the VM.
Select the virtual machine in the vSphere inventory, then right click it and click Edit Settings.
Click the Add button and then select USB Controller from the list. (You can only add a single USB Controller to a VM).
Now you can connect a USB device – but if the device does not show up then it not supported.
Click Edit Settings again and then click the Add button and then select USB Device.
Select the USB device that you want to connect to the VM from the available device(s). Here you can see that I already have one device connected to a VM already.
I didn’t have a whole range of USB devices to test, and not all of them were detected by vSphere. I did not have any issues with jump drives or even my Logitech webcam being detected but my USB DVD Writer was not detected at all.
Hopefully this feature will only improve with subsequent releases.
Update: My Canon Lide 20 scanner also works 🙂