I wish to comment narrowly on this response. Shoji, have you ever noticed the way that Windows does it updates? The ONLY way you can keep a Windows system from updating is to remove it from the world wide web. Otherwise it will find a direct server or shadow server from which to draw its downloads. It will give you a time-limit on how long it will wait, and then it will just DO it. Is the Windows method something you would call "standard"?
Here is the simple answer to letting the user make a choice. A change to front-end only might not make a big difference regarding program stability. The FE-change-only cases usually mean the stubborn users don't get new abilities. BUT the moment you have a change that requires a BE update, that BE is shared among however many users you have. You CANNOT afford to let a single user hold up an entire organization because they don't want to make a change. That stubborn user becomes a road-block, which costs you and your company time and money while you are forced to sit on your thumbs until this user gets the message. It also holds up progress that might allow the company to work more efficiently than they would have using the older version that lacked certain features.