C-c C-conly evaluates the one function you are on, not the whole file. That was a half hour of frustration. :)
This was similar to chapter 2 in that it took you through an example problem, first creating a simple version and then adding features to it. The most interesting thing I saw was the idea of making a top level macro: deftest. Up until now I hadn't thought about doing that. I would have put the check call inside of deftest so that you wouldn't have to write 'check' over and over. At this point I am pretty sure that there will be no exercises for the lessons.