The Lott is without question the way to go if you want to get the most out of this bore. That being said, there is nothing really wrong with the WM and carefully selected handloads, depending on the intended application. The concerns with the cartridge cited in Post 2 were mentioned by many early authorities, who were also disappointed that it was almost impossible to drive a 500 gr bullet at 2000 fps with factory ammunition.
I'v had one rifle in 458 WM, an older M70 that functioned flawlessly. Of course, Winchester had better be able to make a rifle that will feed the WM. I never did anything serious with it, but spent quite a bit of time experimenting with handloads. I got good results with a 440 gr hard cast bullet - 2200 fps - and I'm sure I could have gone higher. They were sized 459 and being a bit softer than a FMJ, I think they gave a bit more resistance at the throat for better burning. At the sane time, I felt they were probably hard enough for any North American and most African game. I did have trouble finding a good mid-range load. Of course they went off and would have done the job on hogs or deer, but ballistic uniformity was not good, with variations of 100 fps over just a few shots. This may not be important on close range work, but it's not something you want to see.