I have taken perhaps a hundred classes from local ones to week long retreats with classes every day (whew). There are only a few that I did not enjoy. I like the people and hearing from instructors about their passion and every time I get a new piece of knowledge to file away for use later.
The best ever class was Sharyn Craig (now retired) who had everyone in class finish a feathered star from template production to sewing in one day. It was a two day class and she was prepared with a class on LeMoyne Star for those who wanted it. She was clear and organized.
The worst class was Roberta Horton who was having a very bad day. I was merrily going my own way in a freeform type of class and she came over several times to be very critical of what I was doing because I wasn't doing it her way. Never mind that I was happy, working and not asking any questions. She was just rude.
I generally dont take any local classes at LQS's anymore since the focus is normally beginner type classes or a new tool. I dont need more tools. Although I am going to sign up for M. Buvia's applique class at a local LQS since she is known as a good instructor and has won national awards with her work. It is pretty spectacular. I should pick up something from her.
I generally take stash for class projects since I am not sure of whether it will be to my taste. I can always make something again if my stash is not "perfect".