Very knowledgeable and approachable. Her lectures were a bit dry, but she knows her stuff, and can help you know your stuff too! I found self-studying and reading the book to be helpful for exams. Pay attention during class bc she covers material that is not in the text. Little assigned work, it's up to you to learn and understand the material.
I definitely disagree with the other rating - Professor Chen was not the most interesting lecturer (for example, she didn't have any cool demos) but she was definitely incredibly knowledgable... she has four degrees from Harvard and knows her stuff. She's willing to answer questions and usually finds her own mistakes within seconds.
So far the worst teacher I've had at UCSB. The lectures are boring and dull, but that's nothing new in an information-heavy class. The thing that makes this class truly awful is the fact the professor seems to have little to no understanding of the topic. She often makes mistakes in lecture and will take 5-10 min out of class trying to find errors.