David's lectures were incredibly clear, concise, and helpful. I didn't use the textbook as he just posted the HW online, and his lectures covered all the material. As long as you go to lecture and take notes, you are almost guaranteed to get a good grade. Lectures were rarely boring, and if you had any questions, David was very good about answering
Prof. Mokriski did a very good job teaching logic. His lectures were very helpful to understand the material and he was always open to questions during the lecture. The class itself is fairly hard, but the textbook helped make the class easier, so definitely buy the book. Grade was determined by HW, Midterm, and Final. HW was graded for completion.