I'll echo what has been said in numerous posts above me. 100% Repair should be available but only at higher level/quest based or faction based with high reputation.
The main reason I agree with the ability to repair items to 100% though a particular vendor is that not everyone is going to pick the repair skill in their character builds, and no one skill should be important above all others that it is a "must have" skill, since we can only realistically tag and raise a handful of skills in NV.
In other words, I want to be able to raise a Doctor/Diplomat/Unarmed type without having to rely on vendors that are stuck at 50% repair across the board like in FO3. That kind of repair should be saved for the backwater vendors. I want to be able to take my gear to a vendor and repair up to 75-90% in a major city and/or settlement and get up to 100% at one of the major factions once I have high reputation with them.
It won't invalidate the Repair skill, since you will be saving tons of caps repairing gear on your own and will have the convenience of being able to repair your gear in the field, even in the middle of a firefight, which is something that a character with low repair skill cannot do.
That's my 2 caps on the subject...