I just finished a course last weekend with Adventure Out and found it great. You get more comprehensive teaching with someone you are paying than with someone who would prefer to be climbing rather than sitting at the base of the crag all weekend talking.
I have also learnt a lot from other people I have climbed with over the years, however there were reasons for needing to pay for this course.
The most important thing I think, regardless of who you learn from, is never take one person’s word for anything (including mine). Do whatever you can to understand what you need to know (knots, anchor selection etc), ask many people and make your own, informed, descisions.