General consensus from owners is: They are not up to American standards of fit or finish, but they make excellent shooters.
It's unknown how durable and long lasting they are.
As with all Chinese firearms, there's always some question about the quality of steel and heat treating for long term use.
Some Remington parts will interchange, and many accessories will fit.
Barrels WILL NOT interchange, and you have to take into consideration the different length of the magazine tube when buying a magazine extender.
Basically, a standard extender made to fit an 18" barreled Remington will stick out past the barrel of the Norinco by quite a bit.
In short, a good truck or HD gun, but nothing to show off to your buddies or pass down to the kids.