If you create a new account, it will allow you to select an @outlook.com email address. There is no ajax on the account name, you'll have to enter the captcha to know if your chosen email address is available.
- Click your username in the upper right, click sign out
- click the 'sign in' button on the next page
- click the white 'sign up' button on the bottom left
- see @outlook.com text box four entries down
Yea, re-typing that captcha about 9 times was the most annoying part. (I only tried 3 different addresses, but it didn't like what I typed in the captcha the other 6 times.)