How ironic that this bug affects the only really secure locking method. Neither the pattern nor the pin are really safe to protect a device as both are easily snoopable.
Security is not an absolute, and there is no such thing as "really/totally/completely secure". The different locking methods allow you to strike a balance between security and convenience that's appropriate for you. All of these are useless against a determined attacker, for a given level of 'determined'.
Edit: Unfortunately I can't find the specific study I was looking for, so I'll have to add my own [citation needed]