Rabbit,
It is only partially true that "The only thing different between now and the wood days is the amount of hard court tennis being played." The other major difference is frequent change of surfaces, hard court to indoor, then to hardcourt, then to clay, to grass, to clay again, to hardcourt, to indoor, to clay, etc. The studies have shown these two factors are the main cause for injuries.
There is no question hardcourt causes joint problems in the long run. From my personal experience, I have no problem play on hardcourt, for now, maybe problem down the road. However, I felt muslce pain after I switch to clay or grass from hardcourt. It is not because clay and grass are harsh on your body, it is because your body isn't used to clay and grass. Your muslce reactions are different to hard court than to natural court.