Medicine & our Future

I've read a few posts here lately. Some interesting, some very far from it. Many recent posts have included expositions on evolution. As such, I was wondering what the lot of your thought about this statement (not necessarily one I've accepted or rejected, yet):

The technological advances in medicine have greatly expanded the human lifespan (at least in developed countries). As such, humans have effectively stunted evolution by curbing "survival of the fittest". Won't the fit & un-fit live equally long? If there was a way to "see" evolution, would it appear to be slowing?

(Ignore money, or any other reason that health-care isn't obtainable ... i.e. say we're in a developed country with free healthcare.)