Did not say it was a fault, only that it impacts the TCO and contributes to a throw away mentality. Compare a Macbook Air with a Protege R600 and tell me its a design feature not to have a replaceable battery, absolute rubbish, its a feature purely to ensure the lifecycle of the device is shortened and the replacement cost of a new battery is better spent on a new device. I am also not suggesting the iPAD will replace notebooks, just has netpads have not replaced notebooks either.
The capacity of the non-user changeable batteries is significantly higher than the user changeable items of a competing PC product.
The Apple batteries in these devices have proven to be exceptional. And as for user-changeable? there's a few screws, whole case comes off, and you bang in a new battery. Sure, it's not the same as switch n go, but with higher capacity and longer cycle life, you don't need to as often either.
And if you don't use a laptop as a laptop, your battery will suffer. Classic example - my MacBook Pro (2008 so the changeable battery model). Got it in March 2008, and the battery is absolutely toasted. It's been used primarily as a desktop replacement, and has lived on a power cord for most its life. I can't get more than 90-100 minutes out of it (minimal screen and wifi on). My December 2007 Macbook, which has been used pretty much only as a laptop (and has a far higher cycle rate and health percentage) will still regularly get up to 2 hours in similar configuration.
When it comes time to buy a new notebook, the 'user changeable' issue is a moot point. Everyone coughed about it on the iPhone, and people certainly have had no problems with that. And with most a/c getting a/c (pun intended) in flight these days, it's becoming less of an issue.
*edit*
Just as an example,
http://www.ifixit.com/MacBook-Parts/MacBook-Air-Mid-2009-Battery/IF188-044 shows you how accessible batteries are on the Mac range. ifixit.com has tear downs of every apple device, along with the parts/tools required if you so desire to purchase, to DIY.