I have more than 4 years experience and 7 other AWS certs, so I didnt use any other resources other than this, since i have enough background and domain knowledge. The questions and contents are very good, taught me things that I didnt know, especially about the code* tools which i never used before. There were some questions from this in the actual exam also.
However, the UX of the portal is very bad. Its too slow, and the menu and contents are all across which makes difficult to navigate.