Illya Kun is an amazing professor, and I am really glad I took a class with him. You can tell he really cares about his students, and whether his students are learning or not. The class atmosphere was very upbeat, and you felt free to ask questions about even the most random of things (like dozens of different words for hats, or the usage difference between a perfective and imperfective word, or what some random slang you heard in a song means). He doesn't give up on students, which I think is even more important for small classes like those in the Russian language department. Illya puts in the extra effort to help all of his students succeed, and I really appreciated that, given how difficult a language Russian is. Plus, he's funny, and has lots of interesting cultural stories about Soviet Russia, and Ukraine, so you'll learn not only about the Russian language, but the culture as well.
If Russian is not super easy for you, but you are invested in getting better, you should definitely take a class with Illya. He's very good at recognizing what a student knows and doesn't know, and helping accordingly. But not in the kind of way that makes you lazy. If you are already really good at Russian, or the kind of student who likes a more focused, regimented kind of class, you might be *slightly* annoyed at how often the class will digress into discussions that are fascinating and highly technical, but not ultimately useful for your grade. These digressions, though, are wonderfully informative.