This is a fairly comprehensive tool, and I could see the value in it as a review tool, especially. The resource is colorful, but not distracting and both neat and organized.
I don't know that it would work as well as an introduction to the words, as the first quiz comes up before any instruction or background is given. If the first quiz is intended as a pre-test, it would be nice to add the ability to easily go back to take it again after going through the entire vocabulary lesson.
I might also recommend changing up the order of the questions a little bit. In the second quiz section, there were always two questions in a row with the same word as the answer. Mixing them up would require more careful thought and consideration, I think.
Overall, this resource was very easy to use and follow. The idea of breaking up GRE vocabulary words into several manageable chunks is a fantastic one, and this resource fits the bill.
I had a few issues with slides not advancing on the first click. If they didn't, they advanced when clicked again. This seemed to happen in the Root Review.