Duffner was a great teacher, who was cool and understood his material. Students shouldn't blame him for teaching the first AP available to students at Longwood.
AP Chem was definately a hard class and Mr. Duffner did help us a lot with it, still wasnt clear and understandable, although that could have been the course.
Don't confuse the course difficulty with the teacher's personality. He's a REALLY good teacher, and will help you out so long as you try your best.
AP Chem and Science Research were the worse classes, but Duff is a really sweet guy, lol. He's retiring, so give him a break