'Check for updates' button in Android now actually works

The infamous 'Check for updates' button has been around on Android for what seems like forever now but in all this time it has been about as useful as the close door button on the elevator, which most of the time doesn't seem to do anything.
Google developer Elliott Hughes has taken to Google+(!) to inform everyone that the button isn't actually useless anymore. The previous behavior was to check if an update is available and only when the update was readily available to your device and was somehow missed by the automated background check for update will it pull the update.
With the new improved button, the device will now actively request for the update and even if your device isn't in the current rollout group for the update, because you are manually requesting for the update, the update will be delivered to you. This means no more impatient stabbing of the button wondering if you are in the rollout group yet or not.
Of course, this is only applicable for the Google branded smartphones as for other OEMs the OEM itself delivers the update to your device and no change has been announced from their side yet.

Source