Aside from Microsoft's problems with Kin and its previous Windows Mobile OS, there are other questions over WP7.

Developers, so far, have downloaded more than 300,000 copies of tools to help them build applications. Experts noted that the applications already written for the existing Windows Mobile OS must be heavily rewritten for WP7, and some developers are unhappy about that. While some large third-party development houses, such as Travelocity, will build applications for WP7 phones, it's less clear whether small development shops will be able to handle the development process.

"The jury's out," said Paul Reddick, CEO of Handmark, a mobile application developer who at CTIA in San Francisco. "Coming out of this economy, developers don't randomly build stuff."