Ok, so I will only quickly mention this as I find it awesomely cool, but have limited information. But basically, all apps get the ability to store settings and a certain amount of data in a roaming data store. This roaming data store is then synched “up” to Live services, and then down to all the users devices. This way, all settings and app things that makes sense to have identical in all places will just be on all devices automatically.
This means that a setting only needs to be done once, and then all your devices will have the same setting. I do however assume that you can manipulate what settings are synched, but I have to check…
But the roaming data store also makes it possible for an app store synch a limited amount of data using the same feature, for example having you browser favorites available on all machines automatically… Awesome!
Not to mention how awesome it is that you can use the same functionality for your login information. The authentication can be handled through Windows in a very neat way that uses Azure to handle the authentication and returns a token. So all you have to do is tell the system what kind of authentication you wish to use, LiveID, Facebook, Twitter etc, and the system will provide the user with a login screen and handle the whole process. And as soon as the process is done, the authentication token can be stored on the machine, keyed on user and URL. This token is also synched in the way mentioned above. So if you sign in and authorize an app on device A, your authentication token is synched to device B, so when you move over and use that device instead, you do not need to sign in again.
The last part with authentication tokens being stored sounds dangerous, but I assume Microsoft has thought about security a WHOLE lot, and that it is safe as long as you LiveID password is secure. And in that case, the feature is effin fantastic!
That about that!