Best white balance implementation

So I wanted to find out what you think the best implementation of setting/adjusting the white balance of your dSLR. For me, I think Pentax nailed it way back with the K10, and continues on with the best solution, where you can adjust your white balance by the camera showing you what the previous picture you took would look like with the settings you are selecting. With the picture on the screen, the image changes as you change the setting. It surprises me that I have not seen this implemented in other cameras......