Freckle is an abomination, and it was only created for educators to keep students doing busywork. It does not teach anything, and hides behind "review" as an excuse to make students do the same work over and over with no benefit.
My overall opinion about Freckle is one of despise. One of the worst parts about Freckle is the placement system, which abhorrently misplaced my students' skill levels. Every single one of my students was placed at a far lower level than their real skill level, creating boring repetitive work. This is one of the most important things Freckle needs to fix right away. Secondly, another large problem with Freckle is that it does not teach anything. Instead, all of the "lessons" in Freckle are just practice. There is a system for teaching new skills, but it is sub-par at best, and a majority of the time, it doesn't introduce any new skills or strategies and just repeats the ones all of my students have learned.
How I Use It
I have used Freckle in my class multiple times before, met by countless complaints from my students. Afterwards, I tried it myself, and found it a useless excuse for a "learning tool". It didn't teach my students a single thing, and it was relatively useless. The only possible purpose I believe Freckle holds is to keep students busy doing work while the teacher does nothing, which I think is against my ideals as an educator.