i think its a cool idea, but it will probably never be implemented to the point of actually working/being effective

the pros:
if u had a system where the whole AV workforce could centralize their efforts and kill the virus before it becomes a veritable threat, there wouldnt be such a large need for deploying AV software on every machine that exists

easier to organize and work against viri, instead of having a lot of independent groups that use different systems that cant necessarily work together

Indeed, I'd almost postulate that regular viruses--the kind that harm, not the kind that heal--are an important, even vital part of the mix. They are the means by which selection can happen.
what selection would be needed if AV security were not an issue? how would it help to be taking out a computer that cant defend itself from a virus if there wasnt a virus in the first place? it doesnt make much sense to me, but what do i know
i think it would be quite nice if there was one less service running on many computers, and instead have a server that would clean out all incoming viri and send out its own healing virus

that system breaks and a whole lot of people are out of luck (and probably a computer), no one wants that kind of responsibility

users have less responsibility to protect their machines and can be less active in what is going on with their computer, not good at all

is not a security fix all, as many people would initially think, there would still need to be an active work effort against viri

there are a lot of other pros and cons, those are just the ones i could think of off the top of my head. but like i said, its a cool idea that will probably not be realized to the point the creator wanted it to be, merely because of its nature, like a eutopia or anything else that would be even close to perfect or a cure to all viri