I think it's still somewhat useful because the skills that make someone a good X programmer, typically make them a good Y programmer as well. The specific knowledge doesn't translate, but the skill does. I was talking with a friend who does very specific DSP work that requires significant amount of esoteric knowledge, and he said, "With a relatively small amount of training, any good programmer can become a good DSP programmer, and any bad programmer can become a bad DSP programmer."

He went on to clarify that he had worked with people from systems-programming backgrounds, all the way up to programmers who had worked chiefly in VB and this seemed to hold no matter what.