Squidy, everyone else has mentioned everything about battery grip and I agree with all of them, but there is one thing that they have completely missed!

Have you looked at the 1D series camera (1Ds Mark III, 1D Mark IV, 1D X)? As you can see they all have built in grip, do you see how cool they are with the grips? You and your camera will look a lot cooler with a battery grip attached! That's the only reason I have a grip for my 7D