Investigations
Our district adopted Investigations this year from k-8. I used the first version about 6 years ago, it had a lot of holes. This new version has a lot more the of basic math practice embedded, which was the problem with the first series. It takes about 1 year of practice to understand why & how the series is set up. I have seen some of investigations being implemented, but then you might miss certain supporting components later on.
The district I came from held summer intensive workshops for about 2 weeks. It helped to understand how to implement and address possible issues that would come up in the classroom. The district I am in now doesn't have the money and is to large to hold these types of workshops. Hence, I see a resistance towards the adoption.
I'm not pro or con any math adopted material, but I believe that whatever is adopted should be used as developed. And supplement any "holes" you may find with something else.
By the way our other choice for math adoption was Everyday Math. It was turned down because it didn't address all of the math standards.