The login was rather convoluted, and it implored me to keep re-registering my book. So I wound up with three registrations of my book. The system didn't record when I completed a practice test or quiz, so I couldn't access old work. The tests/quizzes themselves were often missing exponents in the answer keys; additionally, there were a few with contradictory answers (on one, it said "(B) is correct... (B) is obviously incorrect", or something to that effect).

It also crashed and booted me in the middle of practice tests twice.