Govier was (as far as I know) the first author to base a text on the ARG criterion for argument analysis and evaluation. It has since been picked up by Ed Damer and others. I used the first edition of this as an undergraduate at Waterloo, and 20 years later, I am happy to see it is still in print. The book is a thorough systematic treatment of its subject, and as close to technically perfect as you can get for an intro text. I refer to it while I am conducting my own classes in Critical Thinking. It's topical focus is perhaps tighter than some instructors may want. Fans of the Brookfield "challenging assumptions" model of critical thinking may find it lacking in treatment of some of the "soft skills" related to belief transformation. What it does though, it does very well, and therefore rates 5 stars.
That said, the only potential issue with the book is that it was initially conceived as a text for Canadian undergraduates in the early 1980s. That is an issue for American undergraduates in 2004 because (a) reading comprehension skills of Canadian undergraduates tends to be a bit higher and (b) reading comprehension skills on both sides of the border have declined noticably over the last 20 years.
Since Govier has not "dumbed down" the book for each revision, students may find that their high school education has not adequately prepared them to read at the college level of reading required to digest this book and its material.