I had the same screenplay reviewed twice so that I could benefit from two perspectives. I have to say that I was generally happy with both readers; in both instances, the readers picked up on things I had not noticed when editing by myself or with friends. However, there were "quality" differences between the two readers. The first gave me the impression that they rushed through my work: their coverage had typos, and they missed certain elements of the screenplay that I felt were obvious. In contrast, the second reader had zero typos, provided a few extra pages, gave a rubric outlining what they were looking for, and seemed to catch everything I intended. Perhaps it is always good advice to pay for two readings. Given the quality differences, I'm glad I did.