I guess I don't understand why someone would want a cartridge that duplicates or slightly betters performance of an already existant cartridge, vis-a-vis the '06 vs 300WSM. The standard argument is that the newer cartridge fits a smaller gun - '.308 sized action'. Well, the .308 already exists and, as has been argued ad infinitum on this and other forums, almost duplicates the '06 - for hunting purposes anyway.
I started reading gun and hunting stuff back in the days of Jack O'Connor and Elmer Keith. Those two guys were at extreme ends of the spectrum in their cartridge arguments, but at least they weren't arguing the differences between two cartridges that, for all intents and purposes, are the same thing.
A 180gr .30 caliber bullet going anywhere between 2700 and 2900fps is potent hunting medicine on N. American big game out to 300 yards and beyond. The rifle is much more important than the cartridge when you are comparing apples to apples.
I suppose what's going on is marketing, pure and simple. These companies need to keep introducing new product to keep making money. That is understandable, but why reinvent the wheel? Why not come up with something totally different? Could it be that the practical differences between bullets travelling around 2800fps - be they .264, .270, .284 or .308 in diameter (given similar weights) are slim to none in N. American hunting situations?
I don't doubt that the .300WSM does all the things Winchester claims, but personally I wouldn't trade a good 30-06 for one. Unless one just wants a new rifle in a caliber he lacks, it seems like a pointless endeavor.
George