The AppleCare extended warranty, to me, is like insurance: if you never use it, it's a "waste of money" but if you suddenly need to, especially if the device is expensive or has a higher chance of component failure, then it can be a lifesaver.
From personal observation, if these devices are going to fail, they tend to happen right away within weeks - if not days - of the initial purchase, so users are covered anyway, including 90 days of phone support and 1 year of hardware warranty. Because iPad users tend to carry their device with them a lot more, the chance for an accident is also higher (as described in several other threads in this forum.)
The deciding factor for me was the fact that you can buy AppleCare right up until the last day of your initial free first-year warranty, so there's no rush to sign up for it right away unless you need phone support.