A very good friend of mine, Lars Olofsson, complained about the tab-order between controls in the ViewModels. The project he is working on uses the ViewModels A LOT. And as the work of developing this system goes on, little changes to the ViewModels get applied and the Taborder gets messier and messier.
He suggested that the Taborder should be made visible to the eye so that anyone touching the viewmodel definition could see if it was ok or not. That was a brilliant idea – why have it not always been that way: