I don't use the others, but I often get confused using Google Maps because I have no idea what all the new/unusual UI elements do.

Once I learn Google Maps' way of doing things, I don't want to have to learn a new way for every other app, too.

More to the point, I'd rather not have to learn how to use Google Maps' nonstandard UI to begin with.

> The rumor is that iOS 7 is going to change to a flatter appearance anyway, so in a few weeks this all might be moot.

That's a good point, because the way Apple rolls out incremental UI tweaks is by changing the standard components in backwards-compatible ways.

If you roll your own components, you have to work harder to keep up.

I would emphasize the word "incremental". If you examine the progression of Mac OS X across the past decade, there are significant changes, but they were done cleanly and incrementally and in a way that was immediate familiar to existing users.

I do not believe that we'll see iOS 7 pick up 'flat design' as defined here.