Microsoft is taking aggressive — some might say TOO aggressive — steps to convince iPhone users to rely on their Bing search technology. A recent addition to the iPhone's search options, Bing has updated its iPhone app, as well as enhancing its mobile search site. In fact, if you're not careful, the first time you fire up Bing, it will try to install itself as your default iPhone search engine.
Meanwhile, the mobile site (which also works well on Androids, Palms, WinPhones, Kins, and Zunes) has both beautified and simplified its interface, as well as adding a method to instantly determine and store your location.
TechCrunch has side-by-side Bing vs. Google comparisons of both their app and mobile web implementations.
Search on iPhone is weak compare to Android, since Android has tight integration with Google's search services.