It appears that someone during the day updated the Windows Phone history area of microsoft.com so you can see some of the details in the coming March Update.
Here're a couple of the items:
- Marketplace improvements. We've improved the stability of Marketplace while you download apps. We've also improved the experience of downloading apps larger than 20 megabytes, upgrading from trial apps to paid apps, using a credit card with an address outside the United States, sharing links to apps via email, sorting Xbox LIVE games by release date, and creating an Xbox LIVE account from within the Games Hub.
- Wi-Fi improvements. We now display your phone's Media Access Control (MAC) address in Settings. (You might need this info if you try to connect to a Wi-Fi network that uses MAC address filtering. To learn more, see Connect to a Wi-Fi network.) We've also removed the limit on the number of Wi-Fi profiles that you can store and reduced the time it takes to start your phone if you've stored lots of Wi-Fi profiles.
You can see full details at Windows Phone update history page. Keep in mind that the update is "staggered"so it won't be instantly available to you if you check for updates.