BIGR: The cartridge came from Ned Roberts,who developed it by necking down the 7x57 case,and used it to shoot woodchucks back here in New England. Remington introduced it as a commercial cartridge in 1934,and it was one of the cartridges for which the pre 64 M70 was chambered when the rifle came out in 1937. IIRC the Winchester M54 was also so chambered.
The "hype" is because it works....
Back then it filled the same niche filled today by other cartridges like the 243 Winchester.etc, ie a general purpose deer/varmint cartridge that recoils lightly,generates relatively high velocity,yet with enough bullet weight to do a thorough job on deer sized game.
A ore 64 M70 in 257 Roberts was the second centerfire rifle that I ever owned,and I used it extensively to shoot piles of woodchucks, crows and fox here in NE.I hunter deer some with the cartridge but the rifle was a bit heavy..this led to other rifles that were lighter....in the early days of my western hunting I frequently took mine and have shot a good many pronghorn and some mule deer with it..
Mostly I have used 100-120 gr bullets on deer sized stuff driven between 3100-3200 fps;120's at 2900 as well, and 75-87 gr at 3300-3400.
I've had that pre 64 M70,a couple of PF M70's, Rugers,custom on Mausers and M70's, Remington MR's and Kimber Montana's and Select Grade.Long actionor short , they all worked well.I think the Kimber and the Rem MR are the slickest factory rifles chambered for 257 Roberts to come down the pike.
I have used the 25/06 as well;it beats the Roberts by 150-200 fps, but generally comes in somewhat longer, heavier rifles,and for the uses to which I put a 25 caliber, the Roberts burns less powder,gets the above velocities in a 22" barrel, is less noisy,and kills as well, near as I can tell..
It's trajectory with 100-120 gr bullets is about the same as that of a 270 or 280 with 130-150 gr bullets.I have used it on pronghorn out to about 400 yards and would not hesitate to use it again under similar circumstances.
The rifles I have had were all twisted 1-10,but if I were to focus on heavier bullets I would not, today, hesitate to use a custom barrel twisted 1-9.
The cartridge got beat up by the 6mm's when the 243 and 6mmRem were introduced,without good cause.I have had more than one Western rancher tell me the Roberts is more gun on an antelope flat than a 243,but I think this was more a function of early 243 bullets behaving erratically than anything else.
That said, the Roberts is a sentimental favorite for me, and my own #1 choice in the venue of 24's and 25's.Were I building strictly a target/varmint rifle I would lean to the 6mm's but as a general purpose deer/antelope cartridge, I like the Roberts the best.