It's not clear yet when Microsoft's newly announced Windows Phone Marketplace is going to launch, but when it does they'll have a bevy of partners already on board, ranging from the AP to Foursquare to Pandora. And they look good!
Microsoft's keynote is all about about Windows Phone 7 apps, which will be a huge determining factor in the success of the phone. Other partners to make it to the app store include Fandango, Sling Media, and Shazam.
You'll also be able to try applications out in the Marketplace before you use them:
The Marketplace features a panoramic design and active merchandising to increase the discoverability of games and applications, and supports one-time credit card purchases, mobile operator billing and advertising-funded applications. The Marketplace will also enable customers to try applications before buying them and allow developers to cross-promote their applications through deep linking.
Sounds like they're trying to trying to make it as developer-friendly as possible. And it makes sense that they'd have to, given that they need to attract as many as possible to an unproven platform in time for the Q3/Q4 launch of the Windows Phone 7 Series.