Tablets were a veritable niche until the iPad, which made Apple's launch easy: it practically walked into a market uncontested. In 2011, however, it's virtually surrounded on all sides, mostly by Android devices such as the Motorola Xoom but also by the upcoming BlackBerry PlayBook and even the left field entry from the HP TouchPad. In our full review of the iPad 2, we'll look at whether it can fend these off and if it can appeal to what could be its toughest audience: existing iPad owners.