I received the newsletter from Windows Marketplace saying that WP7 app submission is open to all registered Windows Phone Marketplace developers. The good thing about it is that you can use one account to submit your apps/games for both the Windows Phone Marketplace and the Xbox LIVE Marketplace. The registration fee is $99 per year.
When I submitted my app, I faced some problems to login but the following steps helped me to solve my problems.
- Go to xbox.com
- Sign in using your Marketplace developer credentials
- Return to App Hub and select My dashboard (Windows Phone 7 or profile). You may need to select this option twice (the first time could give the same behavior, but the second time should work).