Well I used the Kaplan book and when I did the ETS practice test it seemed to have been useful...but boy was I shocked when I wrote the real test! I also did have a chance to go through a friend's Princeton Review book and it was quite similar to the Kaplan one. I felt so prepared and after words I just didn't know anymore!
I found a lot of terminology was nothing I had learned in my 4 years of undergrad work, although I am Canadian and I am starting to wonder if things are a little different...however I doubt it due to the fact that most of our texts are American published.
I guess my biggest issue was that the study material didn't seem to be an adequate preparation...:(