Support for Multiple Users on same device Is there such a thing as a "current user" on Android and a way to switch it?

I'm interested in getting a Motorola Xoom and would like to share it with my wife when at home.  For my Windows laptop we us fast-user switching so that we can keep our own tabs and logins.  I'm not specifically interested in the privacy aspects of user-switching, so if the OS doesn't support separate users, is there a concept of profile switching?
This is available for phones starting in Android 5.0 (Lollipop):
http://www.android.com/versions/lollipop-5-0/

And for tablets starting in Android 4.2 (Jelly Bean):
http://developer.android.com/about/versions/jelly-bean.html#42-multiuser

As Tatjana Heuser mentioned, it's also available as hidden functionality in Android 4.1, but not accessible through the regular user interface.