I looked at MathUSee and decided that I didn't want to use manipulatives for every single lesson.
I have been looking at Miquon math (uses some manipulatives) and Singapore. I have heard and read many testimonials about Singapore. Sounds like you need to start with that by second grade for your kids to really get it, but, it seems like the best program for actually teaching the kids math. Seems like many like to team Miquon and Singapore together.
You can do a search for online testing for any of these math books so you know what book to place your kids in.
My son tested into 3rd year Abeka (lame math in my opinion) 2nd year in Saxon (I hear from many it is very boring) and tested 2nd in Singapore and LifePac. LifePac is good. It does a great job of explaining math He also tested 2nd level in this one. So I too am on a quest to teach math and find the right method. Mathusee looked very cool, but to purchase the items was quite expensive, and it requires me finding space for one more organizational cube.