I went through intermediate level textbooks and workbooks. The materials, are very good for vocabulary, reading and listening. Writing exercises are not bad, but I feel it would be more practical to include more English-Korean translation exercises. Essay questions on haircuts or weather are not particularly interesting. Translation exercises have also an advantage of clear answers, which is good for someone who might want to use the workbooks for self-study.
Since there are lots of exercises, I would also mark the more important ones, which any texbook user must go through if he wants to comprehend information.