My overall opinion on Kahoot! as a learning tool is that it is great for reviews but not very useful for learning new information but I don't really feel like that's what it is designed for anyway. I like that setting one up is very easy to do and the website for the most part is very user friendly. I also really like the ability to share the quizzes and duplicate quizzes you like to make your own edits to. Kahoot! is very useful as a review tool because you are in control of what goes into it and therefore you can focus on exactly what areas or topics your class needs the most help or review with. One last drawback I have is that though set up is easy, it can be time consuming depending on how many questions you want to have.
How I Use It
I most often use Kahoot! in my classroom as a tool for reviewing information before a test or quiz. Kahoot! works well in that it is very engaging for the students (especially high schoolers who can use their phones during class) and it quickly shows me how many students understand the information and which information I need to review further. The one complaint I would say I have is that often students just try to answer fast to earn more points and don't always read carefully which is the opposite of what they should be doing on the test.