Xoom 4G Upgrade Requires 6-Day Mail-In Operation: The Xoom tablet has a respectably fast Verizon 3G connection, but Motorola promises a free upgrade to Verizon's faster 4G network within a few months. To do that, however, you'll need to ship your Xoom back to the manufacturer for more than a week.
I'd call that a fatal flaw. A shame, for an otherwise promising product.