Yes they are good, yes they have errors, you must assume that all non trivial technical documents have errors. I have had technical material on the web for many years and yet occasionally despite millions of page requests (I am not exaggerating) I occasionally get feedback that suggests ambiguity, improvement and very occasionally correction. However Dans material have a good reputation for accuracy, and even better he responds to feedback.
But alas Dans questions they are not the best, the best are definitly mine!!!
