I passed the exam yesterday.
This was one of the most challenging certifications exams that I take so far. It's not just about Spring technology, but it is about general concepts and how and why they are implemented by Spring. That said, I read the documentation and all the books suggested, and to consolidate all that, I made some mock exams. The ones by Ivan Mirchev were the best.
Good questions, good explanation, and, when possible, links to the documentation, which helps even more. This structure was very helpful because reading the documentation is undoubtedly necessary to take this exam.