I've heard of both the cartridge and the rifle but have actually seen one. I know a guy in South Africa that swears by the 7x64. Ballistically both rounds woule be about the equal of the 7mm Rem and the 7mm Wby. A few fps between them won't make much of an impact on game.

I lost my father last Sept to lung cancer. This fall I'll hunt deer with his old 7mm Rem Mag. He bought it in 1963, the year I was born and the 2nd year the cartridge existed.