MIX 2010 started, and one thing quickly grabbed everyone’s eye: Windows Phone 7 Series Marketplace, and it’s sexy. Besides from its charming good looks, it has support for ad supported content, operator billing, and credit card charges. There’s also a try before you buy option similar to what Android has to offer, but developers get to pick the terms and the fine detailed things, like time of trial. The UI looks identical to rest of the well-polished OS and has a panoramic view where the user can see categories and titles, as well as get more information on their app that they’re seeking, including pricing, screenshots, reviews, and ratings.

Who are among the first to launch their apps for Windows Phone 7 Series? Well, these guys:

AWS Convergence Technologies, WeatherBug, Citrix Systems Inc., Clarity Consulting Inc., Cypress Consulting, EA Mobile, Fandango Inc., Foursquare Labs Inc., frog design inc., Glu Mobile Inc., Graphic.ly, Hudson Entertainment Inc., IdentityMine Inc., IMDb.com Inc., Larva Labs, Match.com LLC, Matchbox Mobile Ltd., Microsoft Game Studios, Namco Networks America Inc., Oberon Media Inc., Pageonce Inc., Pandora Media Inc., Photobucket Inc., PopCap Games Inc., Seesmic, Shazam Entertainment Ltd., Sling Media, SPB Software Inc., stimulant, TeleCommunications Systems Inc., Touchality LLC and Vertigo Software Inc

A nice, smooth set of first developers, but unless the platform gets lots of good apps quickly, it won’t be going anywhere. One of the biggest selling points on the iPhone is apps, over 140,000 of them. When a consumer is deciding whether to buy a WP7S phone or iPhone, one thing that they’ll think over is apps. Since apps extend what the phone can do, the consumer might be attracted more to the iPhone if the app catalog is as skimpy as the Zune HD’s catalog.

Oh, and it’s the only way to install apps on your Windows Phone.

We’ll know more soon, and keep checking back for the latest.