I have the standard 8 inch .460 and the performance center .500, both shoot great.
One issue with the .500: the ejector rod will loosen and back out the ejector star preventing cylinder closing. Of course this is specific to this one revolver and not worth the hassel of returning to S&W. As far as scoping, I just put a cheapo Bushnell Trophy Red Dot on it and it has held up just fine. Have found the very best bullet to use is the Remington 385 grain Jacketed Spire Point. They are pricy at about $65.00 a 100, (that is up from $27.00) but dang do they shoot. The .460 is a shooter too, excellent long range accuracy.
That all said, if you want REAL long range accuracy, get the T/C Encor and scope them with the Burris 3X12 handgun scope, They are excellent scopes for long range shooting.