I just bought the enVision Math book for 4th grade as I got tired of my son bringing home unfinished math papers and being unable to do them because the school does not allow kids to bring books home.
The book is okay. It is colorful which I like. My son finds the book slighly confusing (but that could be just for him).
I haven't used the book long enough to give you a well educated opinion... but so far I like most of it.
What I don't like about the program is that it requires explanations as well as answers. Sometimes gifted students know the answer but don't know how they got there. There should be nothing wrong with not knowing how to explain as long as you get the answer right.