On Monday, AT&T and T-Mobile began selling smartphones powered by Microsoft's new Windows Phone 7 operating system, the software giant's first aggressive push into the high-end mobile market. Early signs indicate that the Windows-powered devices are selling briskly. But over the long run, can old-guard Microsoft hope to compete with the cultural cachet of the iPhone and its brethren? (Watch a Windows Phone 7 ad)

Probably so — it's a great product: Windows Phone 7 features "the most aggressively different, fresh approach to a phone interface" since Apple's blockbuster came out in 2007, says Matt Buchanan at Gizmodo. The user interface feels "amazing," and the built-in apps are "almost gratuitously tasty eye candy." Should you choose a Microsoft-powered device over an iPhone? That will become more clear "in six months, after the ecosystem has filled out."
"Windows Phone 7 review: Ladies and gentlemen, we have a race"

It's a good product, anyway: After playing around with Windows Phone 7 phones," says Walt Mossberg in The Wall Street Journal, I would agree that "Microsoft has used its years in the smartphone wilderness" to devise a "novel and attractive" user interface. Overall, the product does have some advantages over competitors like the iPhone — for instance, the built-in Office suite. That said, "I couldn't find a killer innovation that would be likely to make iPhone or Android users envious."
"Windows Phone 7 novel but lacking"

Check back in a year: After a long run-up to its release, it would be nice if Windows Phone 7 had "the fit and finish of a fully realized product," says Joshua Topolosky at Engadget, "but that isn't exactly the case." Though "there's a lot to like or even love in WP7," including "really pleasant" web browsing and "accurate and nuanced touch response," Microsoft still "feels a good year behind market leaders right now."
"Windows Phone 7 review"