I agree that simplicity and elegance are key, but in my experience the UI does not inevitably get messy. The same rules apply, but you have to work at differen

I agree that simplicity and elegance are key, but in my experience the UI does not inevitably get messy. The same rules apply, but you have to work at different levels of abstraction. The central structure and algorithms of a UI are no longer about the data itself, but about transforming the data (and transforming the transformer!). There's a special brand of programmer crack reserved for those who create elegant and flexible UI code.