In the blog post announcing the release for Windows Phone, Microsoft said that it has also created and submitted versions for iOS, Android, and Symbian. It's no surprise that the Android version gained approval first and is now available in the Market, while the other versions are presumably forthcoming. All of the mobile clients offer similar feature sets: joining conference calls quickly, instant messaging, and integration with Microsoft's Enterprise Voice product.

Business users want the ability to choose their own mobile devices, even in enterprise environments. Microsoft isn't the only company making concessions to this new reality, RIM recently announced that it would release software that would be able to manage iOS and Android devices in addition to BlackBerrys. The real question for Microsoft is whether it will decide to make the ultimate concession: Office for iOS.