The Bing app for iOS was decent, until recent updates. It looks like someone at Microsoft decided they needed to make the Bing app for iOS look and feel more like a Windows Phone 7 app. So they did, and the result is an ugly, unusable disaster.
On Windows Phone 7, buttons look like traditional 'labels', but in lower-case font. Clickable elements are very subtly different from text, but yet it's obvious what is clickable and what isn't. The hardware 'back' button, standard on all phones, is used to dismiss modal dialogs. That's how the native interface of the phone (called 'Metro', I believe) is, and it all comes together quite beautifully. Here's what a menu on a native Windows Phone 7 app looks like:
On iOS, buttons looks like, well, buttons. Clickable elements have depth and curves and are strikingly different from text/labels. There is no hardware back button, so Apple has provided built-in buttons with system fonts and colors which are placed on the top right corner to dismiss modal dialogs. Just like Windows Phone 7, it's well thought out, coherent and comes together beautifully. Here's how menus, buttons and dialogs look on iOS.
Good apps follow Human Interface Guidelines of the platform they're built for, which gives them consistency with the rest of the system and makes interactions with the application intuitive. For some reason, the developers/designers of the Bing iOS app decided to follow the Human Interface Guidelines for Windows Phone 7 for their iOS app, instead of following the iOS HIG guidelines, and the result is just awful.
Below is what a modal menu on the Bing app looks like on my iPhone (the rest of the app looks similar, and has the same flaws). I have been using apps on my iPhone for two years and yet it took me several minutes to figure out what I needed to do on that dialog. It wasn't obvious how to toggle options on the menu, nor was it obvious how I could dismiss the dialogs. It took me a good two minutes to realize that the 'done' label was infact a button, and that almost everything on that screen was clickable, except the tiny header that reads "MENU". The font size on that label (page header) is smaller than that on the label-buttons, which sounds inverted, and makes the page look ugly.
Compare this with the image below and notice how obvious and beautiful some of those same options are on the native iPhone mapping application. (This isn't a modal dialog on the native app - if it was, I can guarantee that there would be a blue 'Done' button in the top right corner).
In fact, the entire experience of using the Bing app is so jarring that I refuse to use it at all, in spite of some of its nifty features. And I would be very surprised if I'm the only one who feels that way. It literally feels like Microsoft ported an app that is likely beautiful and usable on Windows Phone 7 to iOS without putting any thought into iOS usability. In fact, my guess is that the developers spent more time trying to make those buttons and table-views looks like Windows Phone 7 than they would have if they just used what the system provided with minor tweaks.
I cannot come up any reasonable explanation for why the designers of Bing chose to do this. If they want their application to be used, I sincerely hope they fix it soon.