According to Kotaku : Now, from the start, players can combine like weapons and repair them to 100% functionality. If you raise your repair skills in this game you are raising your ability to make better forms of ammo and to slow the degradation of your guns.
I'm not really sure how I feel about the change.
In Fallout 3, there was a lot of pressure for every character I played to max out the repair skill early, which felt cool the first playthrough but became tedious afterwards; or just get a no-repair mod, which is also not something I was thrilled about. Needing to scavenge parts for repair is an interesting gameplay idea, but it just wasn't compelling when your options were to either dump a bunch of precious early skill points into repair, or be at the mercy of NPCs that could generally only repair your items to ~40% durability.
In New Vegas, it sounds like there's still an incentive to having a mechanic type character, but it won't feel mandatory. Only time will tell us how it ends up playing out, but for now it seems that it's a step in the right direction.