I can't tell you what the best workshop is, since I haven't attended any. I plan on looking into doing some of them since my schedule is wide open now. But I agree that your frame of mind and where you are at, at the time of class has a lot to do with how good you think the class is. If you think you already know a lot of the information, it won't seem to be a good class because you may not learn anything new. But if you are just beginning to explore the area that the workshop deals with, and you have a lot to learn, then it may seem to be much better, because you learn more.
I look forward to hearing what others say about which teachers they liked and why.