I believe that was what most people were asking for at least I was. I didn't need Apple's auto switching solution. Just the switching graphics cards without having to log out and in was all I was asking for.ATI also can switching graphics like in the new Envy of HP, but it has to be chosen by the user ( which isn't bad since you can make sure the correct GPU is used to your needs )
Letting the users decide which card to use would have solved the OP's request because most of the time people could use the slower card for most tasks and it would give Apple the better battery life they want while the faster performance graphics card can be switched to for the users who need them. This means that Apple could have put in a better graphics card and let the users decide if they wanted to take the penalty in shorter battery life and higher operating temperatures.
As of right now the auto switching does affect battery life because it sometimes picks the better card when it shouldn't. I'm guessing that's one of the reasons why Apple chose not to go with an even better graphics card because it would have lowered the battery life way too much.