Windows Phone 7 A Hot Seller

Take that Apple! Smartphones based on Microsoft's new Windows Phone 7 operating system are in such demand they're selling out—fast.

Microsoft's Windows 7 Phone Revealed

T-Mobile's entry in the Windows Phone 7 race—the HTC HD7—was temporarily sold out Monday.

However the phone, which features a high-definition display and 16 GB of built-in memory—appeared to be back in stock as of early Tuesday.

The demand is a good sign for Microsoft, which needs Windows Phone 7 to be a hit if it's to get back in the smartphone race against Apple and Google.

Gartner predicts the release of Windows Phone 7 will help bump Microsoft's share of the worldwide mobile OS market from 4.7% in 2010 to 5.2% in 2011, but says the company's share will ultimately fall back to just 3.9% by 2014 as competitors Apple and Google continue to gain steam with the iPhone and Android, respectively.

AT&T Wireless is Microsoft's primary launch partner for Windows Phone 7. The carrier is now offering the Samsung Focus and HTC Surround, both for $199 with a two-year contract.

The devices also require a minimum data plan priced at $15 per month in addition to standard minutes charges. AT&T also is offering no-contract versions of the phones for $499. It subsequently plans to introduce a third Windows Phone 7 smartphone, the LG Quantum.

T-Mobile, the other U.S. carrier for Windows Phone 7, is selling the HTC HD7 for $199 with a two-year contract and minimum, $15 data plan. T-Mobile also will launch the Dell Venue Pro at a later date.

T-Mobile's backlog notwithstanding, consumers' best bet for getting their hands on a Windows Phone 7 device quickly appears to be the carriers themselves. Best Buy is only advertising the HTC Surround as "coming soon," while Amazon is already hawking the LG Quantum, but notes the phone is on a back order of eight to nine days.

Windows Phone 7 devices, regardless of manufacturer, will deliver a common user experience based on an interface Microsoft calls Live Tiles. The tiles, six in total, allow users to quickly access calling, social media, messaging, photo, e-mail, and personal applications and services. They also deliver real-time information to the main interface.