If you live near an Apple Store, AppleCare+ is the way to go. Simply make a genius appointment, pay the deductible and walk out with a replacement unit.
However I wouldn't bother with any warranty unless the particular configuration of iPad I was buying was $600+, or I was particularly clumsy.
$500 or less and it doesn't really make sense since you'd be paying 20% of the price of a brand new iPad on the off chance that something might happen to it.
My iPad cost me over $700 after taxes, so for me, the AppleCare+ was worth it.