By far the most interesting part of this release is the new multi-threading features, I recommend reading https://julialang.org/blog/2019/07/multithreading for an overview, and watching https://www.youtube.com/watch?v=YdiZa0Y3F3c for a talk about some unique stuff that's being worked on with Julia's multi-threading (though the depth-first scheduling is not in 1.3 afaik).