Terry, I am impressed that you recognized and gave credit to the accuracy of the prior CPA's work. It seems that in this business when we get a new client, our approach is to look for what the prior jerk did wrong and then post all over the place about how many returns we've had to correct that were done by CPAs, EAs, chains, everybody but us. You gave credit where due, which attests to your professionalism.
We had a client who left a year or so ago and came back because he was disgruntled with his new CPA. From what I could tell, their work was impeccable. I was really impressed that their notes and computations made it possible for me to determine where they had come up with different numbers. The guy has an amazingly complex return--big Sch C business, several rentals in an LLC, etc., yet I could follow their workpapers with ease. They even corrected something we had done wrong in a prior year (guess we didn't ask if one was a commercial or residential rental), and they knew some odd things that I first thought were mistakes but looked up the code and found they were right. They never did compare his QB with bank deposits, though, giving him a couple hundred grand more income than he really had. Also missed the domestic production credit, but I'm not sure they were done when he defected. So yes, we were able to add some value.
We are always reluctant to take on a new client who is disgruntled with their old preparer. Like you, I don't automatically jump the gun and conclude the prior was incompetent. One of the first things I look for in their books and records is to see if the old person got paid. Some jump ship just because they have an outstanding bill they don't want to pay.
Like the other posters, I say DO NOT take on this client. He doesn't listen to good advice and is determined to cheat his employees. Who's to say his accountant won't be next?