I voted classic ring finger as well. Its a gorgeous ring - 'stay classy' as Ron Burgundy would say!!! (OMG - how could I just equate Ron Burdundy/Anchorman with Cartier?! )
I voted ring finger but I really just don't like the look of any rings on the other fingers to be honest. It's a beautiful ring though and I'm sure it will look lovely either way!