What really irks me is that the opposite of skeumorphic doesn't have to be "postmodern fugly".
Absolutely. There are a couple real problems with the ultra flat approach, ala Metro. It reminds many of us of Commodore 64 graphics. Which were okay at the time, because that's all the computer could handle. But now?
It feels like the designers have swung the pendulum so far in the opposite direction that they've eliminated a lot of helpful and attractive design elements, such as the judicious use of borders, bevels, gradients, gloss, and transparency.
Definitely. The world is 3-D. There are shadows and highights. and they can be used to emphasize something, like where to click. We're getting some feedback from that stuff.
I've had a website I've designed flat (hey gotta do as the boss tells us) and people were having trouble figuring out where to click. Yes, there were rollovers, but they had to find them first. So I added a little embossing and a subtle border accent, and the problem went right away.
Skeumorphics, giving us a clue as to what to do. A flat block of color with some words might be something to push, or might be a design element. This thingy over here that looks like a real world button? Maybe it's a button. I use a little skeumorphics in database UI design even. Funny part is when its done right, no one notices. But they "intuitively" find their way around better. Done flat, it is a number salad.
Flat design is only one step away from "mystery meat" web design - a concept straight from Beelzabub to destroy humanity. It is a bad trend in response to overdone skeumorphics, and ends up being worse.