I think Lavelle is an amazing professor. A lot of people will complain about him because the content is difficult (it definitely can be), but I can't imagine a professor doing more than Lavelle does to make sure students have every resource they need for the class. I didn't attend many UA sessions besides the review ones before exams, but I've heard they are extremely helpful if you are struggling to grasp a concept. In his lectures, Lavelle is constantly mentioning how he goes back to fundamentals before he teaches a new concept, and it is actually really helpful for people like me who have forgotten everything from high school chemistry. His midterms are very reasonable in my opinion and he moves at a good pace. As long as you are able to do the Sapling and textbook problems he assigns you should be more than set for the exams.