I don't know what the rest of the reviews are talking about but that woman was rude with me. I'd admit I wasn't her top student but she did do some things I found "wrong" in the academic field. One time after a quiz, she opened up by book and said in front of the whole class, "so quick?" she glances and then says "looks like someone studied." Maybe it's just me but I feel she was harsher on me because I am Chinese and I wasn't one of her best students, she probably expected more from me. I got frustrated when she would comment on my accents and not the accents of other non-Asian students, I know my accent was better. She even gave me a grade below what I needed to enter second level Chinese, what a b*.
Li laoshi is the best teacher I have had since coming to Columbia. Initially, she strikes many students as strict (She IS a Chinese teacher). I think she's better described as professional and demanding -- she won't coddle you, though she's always willing to help. Her class requires more effort than others (coasting is difficult unless you're a native speaker taking the class for an easy A), but for learning Chinese, she's tops. Given time, her bonhomie and genuine concern for her students alight, melting her stern facade with charming Hunan warmth. Truly, she's a great resource.
Hands-down one of the nicest professors I have had at Columbia. The Chinese department seems to prescribe the way classes are run, and I found it repetitive and tedious. Li, however, manages to make the format almost fun, and she has some interesting and amusing stories that spice up her classes. I definitely recommend her.