Wow. Hipmunk is a great example, in my opinion, of how flat can be bad by removing so many visual cues.
The old one is easy to see, understand, and instantaneously "grok", because of the depth cues and shading. The new one is a mess of plain colored boxes, where you have to spend time figuring out what is a header, what is a row, etc. -- it's not instantly obvious. The prices are clearly clickable on the left, on the right I'd never guess they were (if they are). So much flatness just makes the screen to hard to figure out.
Hipmunk really makes the problems of flat design stand out. There is a common belief that simpler design means better UE. The things that are being tossed out in flat design are the things that often made good designs intuitive in the first place though. Many designers are reaching incorrect conclusions about simplicity and the whole KISS principle. The whole KISS principle doesn't require throwing out pixels and properties in the name of "a trend".
Good UE is memorable and intuitive - and is often lacking in the many flat designs I've been seeing lately.
I really fear that flat design trend is making products less emotional, memorable and usable.
The problem seems to be some people tend to do more than flatten their designs dimensionally (as in gradients, bevels, specular highlights etc).
They also 'flatten' the design as in reducing contrast, reducing lines/borders and other ways of separating and organizing information/data.
That's the problematic part to me. Hipmunk did that here.
SeatGeek is an example of almost pure dimensional flattening. It's pretty much the same. Just feels a bit cleaner and more elegant.
Especially notice how they replaced the shadow with a grey border. The shadow played the role of a separator. Thus they replaced it with a flat separator.
What the other kind of a 'flattener' might do is just throw away the separator completely. And that is where you can screw up.
Reducing contrast is really a problem in my opinion for users. I totally agree with you.
SeatGeek is elegant (I like the visual), but as with most flat designs, affordance is a problem. I believe that the word Filter on the right side of Great Deals might be clickable/tappable text (based on my previous flat design button hunts and the previous iOS7 image with a gear). The problem is, I don't know for sure without actually trying it.
When I have to go beyond skimming to discover basic functionality, the user experience is broken in my opinion and cognitive load increases.
> Reducing contrast is really a problem in my opinion for users.
The most terrifying example, in my opinion, is the team selector on the InfiniteHoops app. It keeps the skeumorphic 3-dimensionality of the old selector, but strips out all of the color and context and makes the text hard to read, turning the whole thing into a real mess.
If I saw the "after" UI of Hipmunk without having seen the "before" UI, I would have been totally lost. Where are the buttons? What is a label and what is tappable!? It is even worse with touch, there is no hovering cursor that changes appearance. I honestly think "flat" is going to take a long time to work out the kinks. I think it is here to stay a while, for better or worse.
I honestly think people are making too big a deal about this. The kind of people who download apps are not going to have an issue exploring the UI of new apps to figure out how they work. And it's not that hard to figure out just by looking either. Verbs, arrows, and nouns that don't label something adjacent to them should all be clickable. And if they ain't, oh man, you just wasted two seconds finding that out. Not the end of the world.
Speaking as a 39 year old developer curmudgeon who routinely downloads new apps: I am not going to click around and discover your interface if it isn't obvious in the first few minutes.
As an example, the new flat google maps app is a disaster. It took me weeks to figure out how to do fairly simple things, like how to cancel turn by turn directions. My wife is totally lost, as a long time iphone 4 user trying to use the flat iphone 5 version. When she tries to navigate while I am driving, she is constantly confused while I say, "no! just swipe down hard enough that the app thinks you are going back, then click on the box, then click the x, then swipe up, and stand on your left foot!"
But we have to have a map, so we use it.
As a startup, this is what you should think about: Is your app as useful as google maps? If not, then you can't afford to make it unusable with a trendy flat interface.
Honestly, not a huge fan of newmaps, and I'm a googler. But most people I know have figured out how to use it. I did too after playing with it for a bit. People will figure things out, especially if there are no non-flat alternatives.
The old one is easy to see, understand, and instantaneously "grok", because of the depth cues and shading. The new one is a mess of plain colored boxes, where you have to spend time figuring out what is a header, what is a row, etc. -- it's not instantly obvious. The prices are clearly clickable on the left, on the right I'd never guess they were (if they are). So much flatness just makes the screen to hard to figure out.