If the Xoom had USB host (rather than theoretically might), I would consider one when under $600. The current price is too much, since I will not use the 3G/4G radios, but tether using the Incredible.
Need the thumbdrive function and would be set.
BTW, even the hardware dev that created the USB, posted on the Xoom Motorola support site that he is not sure if it would work or not (thumbdrives and hard drives). That is honest, but nuts at the same time.