Really good professor. Loved his lectures. Final is very fair if you start studying ~2 weeks or so in advance. Wants you to genuinely succeed in the subject and has designed a very good curriculum.

I would highly recommend CS 639 if you're interested in AI and are willing to put in the work. While the projects use PyTorch, it's only used at the tensor-level to use the GPU and you have to actually implement the models. Prof Lee is an engaging lecturer and the final is entirely conceptual. Piazza and TAs are also available for help.