We have been using it for our unit on cells and systems and it has been great.
First of all there is a wide range of videos available for each topic. Most of them are short dealing with a specific part of the overall learning for that subject. I like that!
Elizabeth sometimes has watched them all but a few times only needed 2 or 3 of them to learn what she needed. They are from a wide variety of sources. She has watched Bill Nye videos, medical videos and "teacher" videos.
There is a wide range of activities including matching definitions from the material. These along with the labeling activities are a great review of what she just learned.
The matching activities have a score and so do the labeling. The labeling activities are printable. They include an age range for the quizzes and I have found them to be challenging enough for a middle schooler.
There are many topics including math, language arts, history, geography and a wide variety of science topics.
All this and it is free!