http://www.apple.com/support/ipad/service/battery/
As a point of comparison, my Lenovo batteries that always seem to crap about a few years in cost about $100:
http://www.newegg.com/Store/BrandSubCategory.aspx?Brand=1041...
So... that's a pretty great deal. And I think speaks to how comfortable they are with the battery longevity. Or how fat their margins are.
That said, given some of the probable porno use cases of the iPad...
Will the iPad battery fail before the useful life of the device expires? I doubt it[1]. But if it does there is a convenient procedure for replacing it. Eventually there will no longer be a procedure, but the device will have passed from "useful" by then.
Look at the numbers: Applecare on an iPad runs from month 13 to month 24 and covers a new battery if required = $99. Battery replacement on an iPad = $99. Apple is not expecting significant numbers of batteries to die in two years. (Or they are and aren't expecting anything else to go wrong.)
it has long been the expectation that users are responsible for changing out batteries
And car users used to be responsible for keeping the water topped up in their batteries. That day passed. In an nice parallel to iPads, my Honda FIT has a tiny sealed battery in a unique size. They worked the mass/volume tradeoff[2] and came up with a completely unique battery. (At least they didn't put a pull cord on the dash or a kick starter on the floor.)
[1] My nearly three year old iPhone is just fine and I can still skip charging at night and get through the second day if I need to. The device is about to be orphaned by iPhone OS 4.0. Given the cost of a phone vanishes in the cost of service the only reason I'll keep it is because I have the original, cheaper, plan in place.
[2] I deleted my section on mass/value/cost/ruggedness tradeoffs of glue/screw, custom/commodity cells, and compartments/torsion box. I've covered that too many times before. I'd still love to read an article comparing a handful of devices that make those decisions different ways. My personal estimation is that using screws and having a replaceable commodity battery would add 50% to the thickness of the device keeping other factors the same. It would still be a cool device, just slightly less so.
For example, at some point, I am going to replace my iPod's (5th gen) HD with an SSD and there are multiple vendors and video showing how.
I could get a replacement battery for my trusty six year old iPod mini (still works like on day one) right now. Costs $15 and even comes with tools to open the little sucker up. Let’s just hope the iPad’s battery is not soldered in :)
If you have to send it to Apple, you already can't maintain your own device, regardless of whether they decide to keep supporting it.
I would note that Apple still replaces batteries for the original iPod. And as far as I know Apple doesn't prevent third parties from replacing batteries. What is the fundamental difference between the batteries and another component, like the hard drive?