Ilia is a decent professor. He's extremely clear about what he means and often repeats himself to make his point even clearer. That being said, the class could be rather dull, and it wasn't always easy to motivate yourself to go. His exams (2 midterms and a final) were very similar to the practice tests. The problem sets were straight out of the textbook. If you did the problem sets yourself, and the practice tests, there's really nothing else you needed to do for the exams. He also has a pretty fair policy of allowing up to 2 late days for 2 homeworks and you get to drop one homework (There's only like 6 or 7), so it's not too bad. That said, Ilia is supposed to be a tougher Discrete Mathematics professor than some of the others out there, although I didn't think he was too bad. The class average in the exams was usually between 60-70, but the class is curved so I guess it didn't matter too much.
Disappointing class. I've never had a CS class I dreaded more than this one. A lot of the content of the course was super interesting but it was totally lost through the lecturer. Vovsha's slides were confusing and his classes were extremely boring. Yes, he had maybe two interesting classes where in showed the "magic tricks" but that was about it. I attended every single lecture and tried to be on my A game but his powerpoints were convoluted and his explanations were even more confusing. The class was painful. I tried seeking out extra help through the TAs of the course (generally CS TAs are incredibly helpful and patient). But every other day we would get emails informing us that the TAs would unexpectedly cancel their hours. Like COME ON. (I'm also a TA for a bio class and I've canceled my hours before but every other day is excessive). Also, I've been to multiple TA sessions (I've sometimes woken up at 7AM to make the 8AM session) only to have the TA NOT SHOW UP. SERIOUSLY??? This class was just so incredibly frustrating. Lastly, I do not find Professor Vovsha to be a kind or helpful professor. I went to the review session for the final and I remember asking a question about an intermediary step and why it was necessary. He didn't answer my question and he was extremely condescending. He made me feel so dumb in front of everyone in the review session. I've never felt that way before for asking a question and it prevented me from asking any more questions during the review session. Don't take Discrete Math with Vovsha.
Vovsha is an okay professor. He lectures using his PowerPoint slides (provided on his website) and uses the chalkboard for examples. His explanations are generally pretty clear, although you will have to do some reading on your own for problem sets and exams. Occasionally he does cool demonstrations like a "magic" card trick. He's also an international chess master, so he's pretty smart. His class is definitely tougher than Strickland's. Most people agree that they learned more from his class than they would've under Strickland. Overall, he's okay. But there's really no point in writing a CULPA review for this since he's graduating and probably leaving Columbia anyway.
Somedays he can be a good lecturer. He defines things like a mathematician would - clearly and precisely. However, not everyone is a mathematician, and his definitions can sometimes get lost on me. Most of the time I found him to be reading off the slides, though he is quite helpful in explaining some portions of the course. But he's pretty funny, and he has had more lectures that were good than those that were bad. One lecture was amazingly funny - he performed a card trick that will leave you bewildered, and offered bonus points to those who could solve it (hint: it used the principles taught in class). I would take his class, but also be prepared to study from the textbook. I didn't find the textbook to be that bad, and the combination of textbook and Vovsha is more than enough to pass the course.
Vovsha is a very confident and organized lecturer. He has powerpoints of all the lecture slides he uses and his lectures are NOT just reading off the slides (or the textbook, for that matter). He was able to make the material very clear and genuinely interesting for the class by putting what we learned in context. He can also be pretty damn funny. Overall, if you are on the fence about taking a class with Vovsha (he has a definite lack of culpa reviews), I would definitely say DO IT! You won't regret it.