Andrew Boateng
He's a great guy, but a terrible teacher. I was in his EEE/CSE230 class, and wasn't really understanding his lecture, but figured it might be okay since YouTube and the textbook were available. I was wrong. After seeing that the average grades on the first 2 quizzes were 2.33/10 and 3.17/10 respectively, I decided to drop the class. 

Not worth it
