Though currently in Whistler, my main stomping ground has always been europe and France in particular. I was deeply underwhelmed by the ESF (Ecole du Ski Francais)when I was a beginner and abandoned group lessons after about 3 weeks of holidays.
Things that really made me feel I had wasted my money.
1. No-one told me (until I read it in a book) what makes a ski turn. Even though this was the early 90's, if an instructor had told me the physics that lay behind what we were doing, I would have been more able to picture it in my head. Telling a pupil why they are doing something really helps, otherwise it feels really random.
2. A "one size fits all" approach to teaching. Along the lines of "if this is week 3, I will be teaching this drill". Not every beginner needs to go through the text book one page at a time. I say this, not because it applied to me, but from skiing with friends more recently who immediately "get it", and can , with a few tips and hints, progress though the snow plough (wedge) phase within a couple of hours.
Things that make a lesson:
1. I do think that an instructor who can remember what it is like not to be able to ski can be more sympathetic. He or she can recall the thigh burning terror of standing at the top of a steep blue run, or the things that clicked when taking a lesson when she was struggling. However I am not dismissing people who virtually emerge from the womb on skis as being able to teach and teach well.
2. Understanding people's different learning styles. What works for person a, may not for person b. More experienced instructors get this. I loved the "kick the ball around the corner" metaphor that LY's instructor told her recently. It makes sense to me, and I think I can even guess what part of her technique he was trying to tackle. Here in the UK, I often come across links to a highly successful english instructor (Warren Smith) based in Verbier-he produces videos, runs his own ski school, and features on many websites. I watch them and feel utterly unenlightened at the end. It's important for the pupil not to feel the dummy in this situation-it's the nature of the instruction that isn't working.
3. Understand if someone gets scared!