When the Login Window is configured to display as Username and Password and the machine is bound to a directory service, the 'Network Account Status' icon appears. Usually is yellow or red. Either way, when it appears it is part of the Tab Order, so typing your username and then pressing Tab goes highlights the status icon, you have to press Tab twice to get to the Password field.
A small annoyance, but this behaviour is different from earlier OS's. Does anyone else have the same behaviour?