Since it was unveiled at the Consumer Electronics Show last January, the Motorola Xoom tablet has been hailed as the strongest challenge yet to Apple’s iPad. However, it faces two possible obstacles to widespread acceptance: Its price, and its lack of a WiFi-only version. The Xoom has both 3G and WiFi capabilities, and it’s offered at a price of $800 without a carrier contract. It can be had for $600 if the buyer signs a two-year contract with Verizon Wireless for data services. Apple, on the other hand, offers iPads with or without 3G capabilities.