Nostalgia is nice and I'm sure that they shoot well, but they aren't worth it at that price unless buyers have "money to burn". If that's the case more power to them, I'd stick with the AR-15.
One, yes a better one. I did just buy two Diamondback AR-15 for the price of a single M1. My Armalite Eagle Arms AR-15 cost more, but not sure yet if worth the 2x price of a Diamondback. Definitely prefer an AR-15 over an old M1. Now, if I could buy a functional M1 for $100-200, sure, I would.