I too have a long history with the 7x57. Having read several articles he wrote in praise of the cartridge, bought the first one I ever saw; a Ruger 77. This was at a gun shop in Phoenix in 1972. Ruger had made what was referred to as a limited run of these plus a like number chambered for the 257 Roberts. So, ok I found one of those too!
Then the fun began. I took the 7mm on a Coues hunt that fall and got my first real trophy Whitetail, I still have the mount. This was followed by a nice Mule Deer on the Arizona Strip, A 6 foot Black Bear, numerous Javelina, Columbian Blacktail, well you get the idea.
As for the 257 Roberts, a 16.5" Arizona Pronghorn, several Javelina,some Coues and a Rocky Mountain Bighorn in Eastern Arizona that completed my Grand Slam!
Thank God I have never had to limit myself just one of these two rifles/ cartridges. They have proven to be excellent mountain rifles, just as Jack said they were!