Singapore math is a great product for our family. It is very straightforward and easy to use. The explanations in the text are very easy to understand, they give multiple ways of working a problem, and there is enough repetition for my kids to fully grasp the concept without overdoing it.
This is actually a review for all Singapore Math Standards Edition levels. We have used 1a - 4b with great success. My kids learn new material fairly quickly and do not need a lot of repetition to master a concept. Singapore provides just the right mix of practice without excessive repetition that we need. We use the textbooks for instruction and the workbooks for practice. We don't write in the textbooks and I pass them on to the next child. One of the components of this math program that makes it stand out from others is the multi-step/level word problems. These problems are like nothing I have seen in any other math curriculum. If you have children who need clear step-by-step math instruction with a lot of practice, drill and review, this program is not for you. If you have kids who thrive on problem solving, work well independently, and pick up on new tasks easily without excessive drill this is the program for you! One caution, these books tend to be at least a semester ahead of many other programs. If switching, I would advise taking the placement test online first to ensure the best fit for your child.