Re the built-in batteries. I think many people would probably fall into the category of owning an extra battery *because* they don't last long enough. So by making a built in battery that lasts long enough, they alleviate the need for a spare.

Or they want to be able to replace the battery when it begins to fail to hold a charge. But of course, the new batteries hold their charge for 3 times the life of the old ones.

I'm with you on this Bart, I think Apple have thought really hard about this and have got it right. The only downside I see is if that battery fails, you're up for some pain for a while. But then the same could be said for numerous other components of the system failing.