I don't think it'll be too missed since it seems to be replaced with a ridiculously large customization system, and honestly it didn't add much save encouraging you to carry multiples of every weapon.
It did add to realism, but if you just carried enough weapons you could keep everything at 100% permanently, and it isn't very realistic to carry around 7 hunting rifles at all times.
It also required you to have gain a copy of another weapon once you found an upgrade since most weapons are found in awful condition.
Again, not very compelling gameplay to finally find a combat shotgun, only for it to be not an upgrade at all until you can manage to find a second one. It's just dead weight in your inventory until you do, and once you have it up to snuff you've got to dedicate even more inventory space to keep it functional.
In my hundreds of hours playing 3 and NV, I've never once broken a gun unless I deliberately shot it out of an enemies hands;if the system was gone the only difference would have been a few dozen pounds of repair kits of duplicate weapons.