Took CS61AL (Lab version) about a decade ago. Even knowing how to program and working in industry for several years it was not easy. I think my class was one of the last to use Scheme before they switched towards Python and was entirely taught with SICP Book. Probably the biggest difference between sort of traditional programming courses and CS61AL is you have to essentially understand and do recursion day one. It sort of blew my mind compared to the way I learned because generally you do simple statement programs, then functions, then for, while, do while, etc. Then finally around maybe chapter 10 in a traditional book you get to recursion. CS61AL, SICP, and its lots are great, but they very quickly touch on discrete math and calculus concepts and how they relate to programming/CS. Ditto for first-class functions and Lambda's, all introduced very soon in CS61A. Great course though, was a serious challenge from something I thought I would skate through. Definitely made me a better programmer.