I looked at it, I could imagine being interested in such a site, but I was not able to see anything I couldn't find by Yelp or Google.

Some questions I might be interested in finding answers to:

* Does this church have large number of single people in their twenties and thirties?

* How intellectual are the sermons?

* What, overall, are the priorities and personalities of the people who attend there?

* What does the church think about [women pastors|gay marriage|etc.,etc.]? Does everyone there agree?

I would suggest looking at OKCupid for ideas. OKC, as with all online dating, has its faults -- but it is good at figuring out what you are looking for and then showing it to you. Such a model might work here, as most churches don't share a dater's desire to be selective.