I am a software developer by profession and also currently taking another course called 'Analytics Edge' on edx which uses R, so personally I didn't find the assignments exceptionally challenging, but with just enough difficulty to be engaging. I did find the lecture material to be very, very dry. Though thoroughly explained, its all slides and very little actual coding demos. That said, it's a good overview of the nuts and bolts of the language (more like a crash course), though could be delivered better. I am taking it as part of the specialization.
With that said, this course is NOT for people who are programming for the first time. Since the instructor just focuses on a series of disjointed features and details of the language, I'd say you'd have to have some experience writing code in order to appreciate the nuances of the language and know how these can actually be applied in real world programming scenarios. If you are just starting out coding and taking this course, its very easy to get lost in the weeds.