I prefer the bigger size too when the camera is in my hands. But I do topside photos in certain situations where the smaller size is important. Everybody who has used a 10D knows the 5D size already. The 5D is just a few millimeters wider and due to the uncropped full size viewfinder about 10mm taller in the middle.
For me the 5D is perfect in terms of size. Small if it is important and with grip the right size if I want it (long telelens, vertical shooting, etc.).
There is a size comparison in the white paper between 5D (without grip) and 1D series (pic attachement).
Julian