I work for a faith based hospital and purchased the guide. It is one of those directories whose information is also contained in the Foundation Center resources but I purchased it to have something that can grab and quickly hone in on the faith based funders. Like the Foundation Ctr products it has alot of funders who are "pre-selected" or don't accept proposals. Because of this I keep it for several years because the info is not going to change that much.
I have found some funders that have supported our hospital. So it has helped.