Would the recoil be too harsh for the shooter to shoot accurately, or just too harsh for the gun to shoot accurately after a few shots? You're talking to someone who has to fire .30-'06's and .300 Winchester Magnums quite commonly. Recoil doesn't phase me as much as noise anymore.
I was actually thinking about getting a Beeman springer one of these days whenever I move up to a VERY nice gun. I'm not much of a fan with pre-charged pneumatics. I've seen those Dianas as well. It's gonna be a while before I save up the dough, though.