Yes
MGMAT SC is a def worth its weight in gold. It is by far the best SC book out there.
However, I do want to state that the
MGMAT book in no way gurantees 90-100% accuracy on SC's. The book is very good, but does not cover every little aspect you will see on the exam. I believe this book is essential, but unless you are already amazing at grammer, you are going to need more than this book to get a 700+ on the GMAT.
For one thing the book fails to mention anything on elipsis. I didn't even know what a gerund was until I read through the Kaplan blue pocket book.
The Kaplan book is not amazing, but it does cover a few little extras that you won't see in the
MGMAT book. I've not ventured to Man. Review, Veritas, or PR.
Again this book is essential and anyone serious must have it. But I just don't think it the magic bullet for 90-100% SC accuracy.