I have done the first 3 parts of it. What I can say is that it won't help you a lot in Competitive Programming because the course stresses more on proofs and analysis of algorithms rather than problem solving.

In my opinion, the course is quite good (I have only taken the first course). While it is true that formal parts are stressed more than practical parts, I think that in terms of CP is also quite useful. Maybe, in the short-term and depending on your level, in order to improve your CP level it is better to use other resources, but in the long-term I think it is quite profitable.