jlowell,
Just like doctors, lawyers, plumbers..............There are good ones and bad ones. The more ratings they have, the more they will charge. I would get someone for sure with CFII/MEI. ATP is so they can fly for airlines. The issue I always had was that many will only demand minimums be met in terms of precision, knowledge etc. So if you get a sloppy instructor who doesn't demand much from you, you will carry those sloppy habits with you. As I went on to more professional jobs, they really sharpened up my precision. I wish I they would have demanded that of me earlier. Also, get a guy who is good at teaching and likes teaching. Some of the guys think their mission in life is to be the next Don Rickles. You don't need that. If you are doing this for personal or business versus airline job, you still will be glad if you do it to perfection. I had a guy in training once tell me, "let's do a steep turn, 45 degrees on the bank, +/- 80 feet on alt is below average, +/-40 on alt is average, and +/- 20 feet on alt is above average. No one ever told me that when I was getting my earlier ratings but they should have.
Good luck, Check Six