We used Horizons Math 3 last year with my third grader. Someone else may have a different review, but here's mine.
I don't know if these are pros or cons, so I'll list them together and let you decide.
[*]The book is very colorful.
[*]The teacher's manual has the answers and something else that I guess is a lesson plan or shows what you're covering. I didn't know how to use that part of it, but I know some homeschoolers have to send in reports or something about what skills you're covering, so this may help you.
[*]The book seems to jump around a lot. One day you may be doing simple addition and the next you're doing complex (double digit) multiplication.
[*]It could be done independently. My son needed a lot of help with this math curriculum, but some students could do it on their own.
[*]It was easy to use. The only thing a teacher needs to do is homework help.
[*]The pages are easy to tear from the book if you like giving them separately instead of the whole book.
[*]The book is sturdy and takes a lot of use and abuse from the student.
[*]It doesn't help you teach math. It's just a math workbook...unless you know how to use the teacher book better than I did.
I can't think of anything else. The reason we didn't enjoy this curriculum is because it jumped around. I wanted a mastery curriculum and this wasn't it. We ended up dumping the book part way through the year and focusing on multiplication facts mastery.
This may be the perfect math curriculum for you, but it wasn't for us. If you are looking for a mastery curriculum, look elsewhere. If you are looking for a mixture of concepts for your child to review often, then this might be for you, especially if you're good at teaching the concepts behind math.
My son had gone to public school K-2 and I struggled to teach him the way I was taught, while he was taught differently in school. That also may have been an issue with us using this curriculum. I was trying to reteach him to do it a different way (touch point vs. number line, for example) while trying to use this curriculum.

