Yes definitely buy it! I bought a 257 Roberts in the 80's in a Remington Mountain Rifle which I gave to my daughter when she started hunting. She has killed a lot of deer in the past 16 years with it plus wild hogs, sheep, and antelope. We use Barnes 100 grain X bullets or Nosler 110 grain Bonded. She shot a big bodied white tail with it this past December and he didn't go far.
For years I tried to find one of the M-70s like you're considering and couldn't find one in the condition and price range I was in. So in about '06 I ordered one of the new M-70 FWTs in 25 WSSM and the super short action. It is a great gun too. Then this past fall I found a good used M-70 FWT from the 80's in 257 Roberts and bought it. It just loves Hodgdon H414 and Barnes Triple Shocks. Shoots nice half inch 3 shot groups at 100 yards.
Megan is a hunter not a gun crank like me, she doesn't get wrapped up in paper comparisons of cartridges and velocities and such. She knows that anything she hunts with her Roberts is going down. She goes to her big gun, 300 WSM, for Moose and Africa but her Roberts is her hands down favorite.
A couple pictures in her living room: