Here is an article about the comeback of "classic" worship styles: Modern churches add traditional music.
I am a strong supporter of contemporary music in church. But I also recognize that there is something unique about the hymns. There is not one single contemporary song that seems to have the "staying" power of the hymns.
I think part of the problems is that people feel they have to choose. Either we do contemporary music or we do hymns, but we can do both. I like hymns. I musically rearranged a few hymns. But I also like the classic arrangements.
This also makes me think about the role of inter-generational worship. If there is a "classic" service, and all the older folks go there, are there times when older and younger are interacting? The older generation is less relational, and having another service could encourage their alienation from the younger crowd.