I also remember learning Scheme and having it be a real mind bender. Scheme/Racket is great, but I think Clojure being more opinionated and being immutable by default is a huge improvement in terms of understanding larger projects. Also, their parallel computation and mutex constructs are some of the easiest to understand AND easiest to guarantee you did it right. This is going to continue becoming more and more important given the huge rise in CPU core counts both on desktops and in servers.