The main problem with this book is the overwhelming size of the units. This not only makes it quite difficult to work through the exercises since you have to digest so much morphology to be able to do them, but it also means that by the end of the book, though you will have a good grasp of syntax and morphology, your working vocabulary will still be quite small. I also found the order in which the grammatical concepts are presented to be somewhat unnatural - the subjunctive and optative are introduced before you have a good feel for the indicative mood and its endings. The verb forms are presented in such quick succession that I ended up not feeling very comfortable with them.
On the plus side, though, the basic concepts morphology and syntax are explained very thoroughly and clearly, and the vocabulary notes (usage notes on each individual word, possible alternative meanings, idiomatic uses, etc.) were quite helpful. There were also plenty of drills and reading sentences for practice. Overall, I'd say this book might be well suited to its original purpose - a workshop setting where all of basic grammar is covered in 6 weeks - but for the general reader it is a bit too dense. For the aspiring self-taught Classicist, I'd recommend Mastronarde. I myself ended up switching over to his book after 10 units of Hansen and Quinn, and find it to be better balanced overall, with shorter, more approachable units, and better organized chapter vocabularies.