My son likes it.
We never did much grammar before so I got this to catch up and so far I think it will do!
I was going to do it over the summer but changed my mind, we will do it during the school year and take our time.
The lessons are pretty short (we did only the first 4 lessons so maybe they get longer?), we do all online.
Each lessons starts w/explanations. It gives you a score at the end of each lesson and we start over until he has at least 89. The repetion helps to get the concepts.