I go along with Clive on this one. If the subject suits the full frame then fine, but otherwise I will happily crop. I remember a long discussion I had with Foxy and his crop to fixed aspect ratio's if he had to. Hours later and both sides of the argument remained valid so I think its down to personal style/preference.
I guess Jim and I would have the same argument as he is a non cropper and I respect that, but then I got one over on him by lending him a 6x6, so now he is having to learn to compose square with that, and rectangular with the D200 on the same shoot.
He is lucky I did not have a 6x4.5, 6x7, 6x8 and 6x9 to lend him as well or he really would have been in trouble.
Don