Google has had an iPhone app for quite some time and now Bing has followed suit. The new free Bing app is available for download from the App Store right now.
News, Maps, Movies
From the main Bing menu, you can choose to bring up News, Movies, Images, Maps, Businesses or Directions. Movies hooks into your current location, allowing you to see what is playing near you and where. You can get directions to the theater or call it directly, which is a nice touch. I would love to see it integrated with Fandango or MovieTickets.com for easy purchase access.
The new Bing app also features Bing Maps, which offers directions, traffic maps and different aerial views of your area. It uses the iPhone's built-in GPS for location support. While not as robust as the separate Google-powered Maps application, this is a nice way to get directions when doing a search for a business.
Bing's news section brings up headlines for national, world and local news stories. Unfortunately you can't really specify what type of news you want to see.
Voice Search
The Bing App for iPhone isn't just a wrapper around the mobile Bing website, it adds some new and enhanced features. For instance, like Google, Bing has voice search that works with directions and normal web searches. In my tests, the voice recognition wasn't as good as Google's -- Mashable was heard as "National" and "Christina Warren" was translated as "Christina Lorenz." For what it is worth, Google's iPhone app understood my intended phrases perfectly.
It's a nice idea, but until Microsoft can improve the voice-to-text algorithm, I'd avoid it for all but the most basic phrases. Even saying "Google" brought up "People" the first time I tried it.
Overall
While this is a valiant effort and an attractive application, Bing for the iPhone won't displace Google any time soon. In fact, I actually prefer Bing's optimized mobile website for many of these features because it seems more natural and works faster. Over 3G, the Bing app seemed to hang and even on Wi-Fi my iPhone 3GS seemed to take a long time to process information.