I used it as a refresher after a spell of a few years doing no Greek at all. I enjoyed it, and went on from the basic books to read A World of Heroes, etc. I found it ideal for this purpose.
There is quite a lot to it, though, and I think that if you want a good grounding in grammar, you might do better with a more traditional text book. If, however, you want to be able to read some Greek quickly, then it is as good, if not better, than Athenaze.