Skeuomorph: an object or feature which imitates the design of a similar artefact in another material.
There have been far too many lines written about this subject, poo-pooing the idea that skeuomorphic design elements were introduced into iOS and OS X. But I think that the focus should not be the choice – but the lack of choice.
Every user is different, and come to the Mac from a different background. I would say that the skeuomorphic design helped the less technical/computer aware to become familiar with an application by mimicking visual elements from the familiar. For those more technically/computer literate, it was a (c’mon now – minor) irritation.
But the main irritation was that you had no choice. And now, all that work would appear to be shelved soon, when Apple are missing the chance here to do a sensible thing – offer choice. Allow those that want to have a skeuomorphic appearance, whilst others can have the default chrome, or whatever appearance Jonny Ive wants to conjure up.