JF, it really depends on the references. There are times when the phone calls were useless, but there have also been many times when I obtained VERY useful information from the references.
For example,I once called a very reliable and well-known reference (amongst other things the ref. is an expert in Hilchos LH). He asked me what I am looking for, and when I said I do not want someone who is controlling, he told me the guy is not for me.
There have been other times when I asked if the guy had any psychological issues and I received honest answers (worded carefully in order to avoid LH issues).