Eh.. I think it's only more usable if you're coming from and are used to a traditional desktop like Windows. If you were introducing someone to a computer for the first time, GNOME 3 is by far the most simple and easiest to use desktop on the market right now. Yes even more usable than windows 8 for someone who has never used an OS before.

As for configurability KDE has quite a few more years under it's belt, so it's not a surprise, but GNOME 3 is all JS and CSS so I would say it's pretty configurable and the number of extensions is only going to increase. I think extensions will become much more stable around GNOME 4.0, when they come out with a full OS [1]

[1]http://www.phoronix.com/scan.php?page=news_item&px=MTE0ODg