I got this book for my birthday last year and have been slowly making my way through it. It probably would have gone a little smoother if the first two languages weren't Ruby and io. I've never used either of these languages and so it took a while to understand how to use them.
I thought the language is interesting but I'm not sure I'd be willing to use it in pro duction for any large projects.
This language was very strange and led to a lot of frustration. The community is small and it was difficult to find information when trying to figure things out.
I like to write tests for two reasons: to make sure the solution is correct and to remember how to use it when I go back to it. It was difficult to figure out how to test some of these because the languages were new to me. I didn't really look into learning a test framework since the problems were small and pretty self contained. I tried though.