The mobile/iPad log-in screen lets you view the most recent users who have logged into the device.
If a user has pending sync items or sync errors, a red "sync" badge will display over that user's profile.
You can also reset your password on this screen.
The bottom left corner of this screen will display which build you are currently on: in the example below, you are on build 135 = v4.0.2 (135)