And this is where Apple's deal with AT&T really pays off: When you say you want the to use 3G on your iPad, all you're paying for that option is $130. There's no two-year commitment to pay $50 a month. Instead, when you suddenly find yourself somewhere with no Wi-Fi service, you can open up your iPad's settings app and buy 250MB of data for $15, or an unlimited amount for $30. You can even tell the iPad to cancel the service when the month is over, so you don't get stuck unwittingly paying for iPad data you're not using.

Signing up for the AT&T 3G data doesn't just help you when you're nowhere near Wi-Fi, either--because AT&T also provides Wi-Fi service at over 20,000 hotspots, including Starbucks stores. So if you're traveling and buy 250MB of AT&T data for $15, you're not just getting that data access, but you're also getting free, unlimited access to all the AT&T hotspots. (AT&T charges $20 for its Wi-Fi Premier plan, and $4 for a single a la carte Wi-Fi session.)

Let's face it: One of the things that stinks about the American cellular industry is that it's been built around a subsidy-and-contract business model. When you buy a phone, it's generally discounted in exchange for your agreement to pay a monthly fee for a couple of years. Non-subsidized devices generally still pay high prices for service, and it's still a pain to cancel. The iPad's 3G service has none of these drawbacks: It can be set to auto-cancel and requires no commitment.

Of course, there are some scenarios where buying a 3G iPad doesn't make as much sense. If you really are never planning on leaving your house with your iPad, don't bother with 3G. If you own a phone that offers Wi-Fi based tethering, so you can share your phone's data connection via Wi-Fi, there's no point in piling on. If you own a clever Wi-Fi cellular device such as the Eddy Award-winning , you're already paying a monthly fee for data--and can share that data with your laptop, iPad, or any other device you can think of.

My point isn't that the iPad with Wi-Fi and 3G is for everyone. It's that a lot of people may commit to a Wi-Fi only iPad without considering the flexibility of the iPad's 3G system and the great deal Apple has extracted from AT&T. For an up-front commitment of $130--the cost difference between the Wi-Fi and 3G models--you give yourself the freedom to buy 3G data whenever you need it, without any of the typical cellular encumbrances. That's pretty cool, and it's worth considering when you're deciding which iPad you want to buy.