I was in the iPhone app store and discovered this: Bing was the number four free app on iTunes. That puts it ahead of such venerable iPhone apps as Facebook, Pandora, Google Earth and the Google Mobile App.
I really like it quite a bit. There are some things here and there that can be improved; but it's impressive as a version 1 and works well, including voice search.
It would seem that the iPhone audience is responding well to the app or at least taking it out for a test drive.