Personally, I bought a 6x6 so I could shoot square. I'd rather buy a square camera than crop a rectangle. I think the square format really is a challenge compositionally, especially the landscape. I have always thought of the viewfinder as a space to fill until I have this intuitive reaction that it's 'right'. Which is why I like to print full-frame and in the format of the camera. I concentrate on utilizing the available space in the viewfinder - I don't ignore it - I emphasize it. For 6x6, my eyes were really opened by Harry Callahans' book "Waters Edge" - really masterful use of the 6x6 in the 'landscape'.

-Mike