I still use ND grad. filters from time to time when shooting landscapes and now with Live View on the 1DS Mrk3 you can manually stop the lens down and see the graduation effect really well on the 3inch LCD. By changing the aperture the change in grad. effect is very noticeable. More so than through the view finder especially when using a small f-stops with the lens manually stopped down.
If you are stopping you lens way down, using the LCD screen/Live View is the way to go with ND grads.
Dave