I've heard people saying the adapter would be a bad idea for the xoom and one should go with the cable. The adapter with a usb cable plugged in seems like it would put undue stress on the xoom's micro usb port.Here is the one I picked up that is working pretty nicely.
http://cgi.ebay.com/New-USB-2-0-fem...313?pt=LH_DefaultDomain_0&hash=item2a0f833089
Do you notice any issue with that using the adapter? I was looking to get one for this very purpose as well as being able to also use an external flash drive.