You certainly have heard about the current shutter vibration issues from the A7r. It is very noticeable only in certain conditions (tele zoom and vertical shooting).
But now Sony goes from one extreme to another because Photoclubalpha got word from Sony that the new Sony A7s has a complete electronic and silent shutter mode! There is no info yet about the possible limitations when shooting in that mode. But that’s certainly a good news for Sony folks!
Addendum: An event better news would be if Sony could provide current A7-A7r owners with such a silent mode feature via firmware upgrade…