One objection is that it gives demonstrably poorer results here than you've experienced. Every school in my district is in Title I status for math. This has prompted the hiring of a math consultant, who has instituted months-long drills at the start of every year in an attempt to bring up test scores, detracting from the amount of time spent teaching the new concepts and skills in the first place.
It may be that EDM takes expertise to administer. What I've experienced with DS6 is that when I don't afterschool him on math at all, and he doesn't teach himself but focuses on other things, he stays at exactly the same MAP score for math; the teaching at school does nothing for him. With Singapore Math, he grasps things nearly instantly and actually progresses (quickly).
One reason I don't like EDM as implemented here, which might be different from elsewhere, is excessive stress on the concrete, use of manipulatives, etc. It's unnecessary for my son, but that is admittedly probably due to the fact that he grasps abstract concepts much more quickly than normal. But that's also why I don't think that EDM, at least without discarding a lot of this excessive handholding, would be good for kids with a strong math streak in general (not saying anything about your daughter here, please understand-- in fact she may be compensating for the shortcomings of EDM a good deal by sheer talent
).
I prefer an exceptionally clear explanation of a concept, with concrete and pictorial representations perhaps, but without clutter such as description of things as machines when teaching multiplication, etc. Kids don't in my experience need to be babied to that extent. I've also seen an excessive focus on silliness like drills on constructing whole numbers in a bunch of different ways, I suppose in the hopes of building up number sense; this doesn't constitute problem solving skill development or anything really useful in my opinion. This might be due to how it's implemented locally, though.
DS's MAP test was essentially a nullity at the start of the year, due to the fact he didn't have paper and pencil for much of the test. When he tested in the winter, he wound up with a huge advance, but it wasn't due to schooling. At the time he was showing 50th percentile or above up to the ninth grade. His score went down four points by the end of the year. That's why I say he's learned nothing. This is partly simply a big level mismatch, of course.
I guess, to sum up the things I don't like:
- May take more expertise to administer than is typically found, or at least locally found here
- Excessively babyfied, at least in the early grades I've had occasion to see materials for; cluttered presentation of concepts
- Do-work such as constructing whole numbers ad infinitum makes it very yawn-worthy for my gifted son
- Far better options are available
