We really like the singapore math series. I like this workbook and textbook, but I have one complaint. I do not like that they write the problems horizontally once they get into carrying and borrowing (they call it renaming). I feel this makes it more difficult for the new student to execute properly lining up the place values. Because of this we use a separate notebook for the pages where they have not written the problems vertically. Unfortunately this means that I frequently have to copy over entire pages at a time as I have a child who is still building hand strength and will wear out faster (and therefore get frustrated) if she has to copy too much while working on a new concept.
I've been using this series of books with my kinder and 3rd grade children. I like that they really teach understanding of math concepts and problem solving. With multiplication and division, I have had to supplement with additional practice.
I liked so much the book and the whole singapore curriculum that I bought to my kindergaten child to. They love it. It makes math very fun. And we do "math experiments" every day with just enough written practice!!