Vanilla F3 repair = suckage.
However, there are mods that deal with that quite well: they reduce the rate at which items degrade, which is pretty ridiculous in vanilla, and expand repair lists, so you can, for example, repair a Chinese AR with a regular AR. That takes care of the idiocy that is carrying around a hundred guns just for spares.
FOOK2 takes it even further, they intended to implement a system that works with generic parts to fix or sell, which you get by stripping down not just typical items, but "wasteland garbage", as well. So, for example, out of a stripped camera you may salvage a lens for use in a laser rifle. That sort of items are also included in vendor lists, so you are much more likely to find a spare servo to fix your power armor, than a whole suit for sale. Don't know how far they got it, but it sounds pretty sweet.