I received my rescue through Mayflower. (I am in New York)
I found Mayflower to be very professional. I heard of a rescue in foster care and spoke with a representative of Mayflower via e-mail multiple times while waiting for my application to go through. I knew up front that Hardy had no papers, and had never been inside a house his entire life. We knew immediately that Hardy might have been a lot of work and we were willing to work with him. A representative did a home visit and brought one of her dogs to see our interaction with her dog as well as how my other dog would react to having another dog in the house. She had questions to ask us to see if our home was a suitable place for his placement. A few days later we went to meet Hardy at her house. We could see what we were "getting into" and she could see how we interacted with him. Mayflower was very quick with the placement and I think in all it took us 2-3 weeks before we received Hardy (Perhaps less--I had just undergone surgery so the days kind off rolled together). We signed a contract with Mayflower and received handouts on Corgi care, a bag of food, toys and two collars when we took posession. I made a donation to help cover Hardy's vet bills (tooth extractions/worming/rabies shot) It was a very nice experience and I would take a rescue from them anytime.
As I said before, they are very professional and it is easy to tell that they truly care about finding the best placement for the rescues that they take in.