My Take
My students absolutely loved this program! They would beg me to use it. I really liked how easy it was to give differentiated assignments to all students and how it allowed my students to work independently and focus on their unique goals. I also liked that it gives you immediate data to see what students are understanding or struggling with. One thing I didn't like was that my kids began to "outsmart" the program and would get on other random games instead of staying with the eSpark website and pacing, so it does require some active monitoring. Overall, it's a very awesome program and I would recommend it to any educator especially if you teach in the older grades (3rd and above).
How I Use It
I would use this in my 3rd grade classroom during literacy and math centers. One of our stations was eSpark where students would practice whatever skills we were working on.