Our district uses Everyday Math in the elementary schools (K-5). They move on to Connected Math in middle school (6 - 8). I currently have a 4th and a 7th grader and both have gone through the program from kindergarten and have thrived. (I am currently a SAHM but my background is in math and computer science if that makes any difference as far as my opinion goes.) And almost every school in our district scores high on the math portions of the state testing.
The program is a spiral curriculum which I understand but can't explain. But basically instead of teaching everything in one chunk, it introduces a concept, the a month or two later it revisits & adds on to that concept, and then another month or two later it revisits it & adds on again. Here's a link to the web site for an explanation:
http://everydaymath.uchicago.edu/about/why-it-works/spiral/
I actually like that it teaches the kids different methods for adding, subtracting, etc. When my kids were learning the different methods, if they calculated something wrong, they would try a different method to see if they could do the problem correctly with that method, and then they would go back and see what they did wrong with their original calculations. And some methods worked better for my kids than others. Both have worked their way to using the traditional methods for calculations but my oldest will still pull out one of the other methods on occasion if she just can't get a problem worked out the traditional way.
I also like that the program checks that the kids understand what they are doing. Some homework (and maybe even test) questions, ask the kids to solve a problem and then explain what they did in words. (I find it difficult sometimes to do that. I know how to do the problems, but I find that it can be harder to try to explain it.) In my experience, the knowledge sticks with my kids better when they can actually explain the process rather than just do it.
The teachers at my kids' school do make sure the kids learn the traditional methods also. And to make sure they know their basic math facts, the teachers do timed tests for addition, subtraction, and multiplication tables throughout the year. Maybe that makes a difference.
At the end of 5th grade, my older child passed both the 5th and 6th grade end of year math assessments and was placed into a 7th grade math class as a 6th grader. Based on the math testing done last year, she is now placed into a 9th grade Advanced Algebra class as a 7th grader and doing well.
One thing that I have heard from a teacher at my kids' school is that it's not the best program for kids who struggle with math. I can't remember any details on why though. My kids don't struggle with math, so I can't give any feedback from that perspective either.
And I do have a friend whose district switched to Everyday Math when her daughter went into 5th grade and it was a struggle for her. But my friend will also tell you that there wasn't any extra support offered to the students & parents during the transition year. And she didn't feel that the teachers had much support either.