Hi, Bob-
Sometimes, churches can use a non-religious concert to advance their religious purposes, and that makes me uncomfortable. Most times, that's not the case unless the performance is "sacred music."

I guess I do feel a level of discomfort in most church concerts, even in my own church - because I view the space as "sacred space" intended for worship (and on the other hand, I feel very comfortable at the religious services of most non-fundamentalist religious denominations). Unitarian churches and Quaker meeting houses work well for concerts, because they're usually quite devoid of religious symbolism.

-Joe-