This is a great example of the benefits (and limitations) of sticking with the standard controls and features supplied by the platform. You get an easy move to the new UI design style when it inevitably comes around.

But then you can't do innovative things like Tweetbot and other apps did.

The thing I find most interesting, though, is the way all our perceptions about what good UI is change over time. A few years ago, iOS looked fresh and modern and good. And now pre-v7 iOS has a lot of elements that look clunky and dated.

It would be a fascinating study to look at all the things in our environment and society that push these changes. It's got to go beyond just software and into fashion, media, industrial design, etc.

What would be even more fascinating (and there's no way to do this) would be to take designs that we think are great-looking today and take them back a decade or two or even more. Would they look cool and futuristic to people back then or would they just look stupid?