Have you thought about a "Concede" button that could be used to withdraw from again when you have to be away from your computer or when the end is obvious? Sort of like chest when you knock over the King to end the game.
We have all seen games that end up drawn out because of a "family emergency" or someone having to leave town. We would avoid the 24 hour waits with the ability to concede. Speed games would be better if a player who has to leave the computer unexpectedly could concede instead of dead beating.
In games where you have no hope of winning but the other players had been taken you out yet, you could concede. This would be especially helpful for non-premium members need to get the game off their list.
You would lose point with conceding, obviously.