It is! And i highly recommend it.
I agree about the new wildcat thing, but look at it this way... And this is coming from someone who hates the 6.5CM because of the fake magical properties it seems to have developed thanks to the newbies... But a .257 Creedmoor would basically be the modern equivalent the old .257 Roberts AI... And there is Lapua 6.5CM brass everywhere (and cheap Hornady brass if you don't want to pay the premium), It already has the 30º shoulder, and it's only a simply 1-step neck-down to .257... So there is no real fire-forming to do.
That being said, I can see the advantages it would have by using the CM case, versus trying to track down a .257 Bob AI reamer and then multiple necking stages (either up or down), etc...