I think its a pretty good idea. Hundreds of people die from needing organs each year - and this poses a viable solution. Albeit one with interesting ethical issues!
That'll never happen. You have to be in a braindead state, or have brainstem death. Your heart will still beat, thus keeping organs with a supply of blood - and you'll be artificially ventilated. Most organ donors have massive head injuries and therefore have no chance or recovery, and are only kept alive via a life support machine. So rest assured, the doctors will make sure you're pretty fucked before cutting you open
Everyone should try to donate organs though, to not to it just selfish.