5 stars: At first I felt the English was a bit awkward. After a few lessons in Java I don't even notice it. The lessons are great. The difficulty is perfect. I have 35 yrs of programming for engineering effort experience and am looking to brush up on skills. I highly recommend Stepik.
4 stars: Great app, but it would be much better to see the right answer to quiz after, for example, 10 tries. Or to have a button for it, when you won't get poins anyways. When you have 6 options and from 1 to 6 of them can be right, you start to hate it because you want to know the answer.
4 stars: Pros: There are many courses in varied subjects. It's free. Course I've taken has been concise but comprehensive. Cons: The quizzes I've experienced have not adhered to technical, or previously established, terminology. Quiz wording has been ambiguous. Typos. Can't beat a free course.
3 stars: Everything looks clean cut and professionally done, however I found the course selection limited, for my interests. Why not indicate what type of courses are on offer, rather than people having to create an account... etc. Other than that, I can't offer any feedback. Didn't try to access a course.
3 stars: It's from Russia with love, support English but I can't find the course I looking for, courses are limited to a few basics, the app had a connectivity problem or something, anyway I uninstalled it, not such a useful app for me, but I'll give it a try in near future maybe all courses be availab...