Absolutely agree, in my case the difference between studying and not studying for GRE was more than 200 points for each section.
I think verbal section has the most potential for improvement, since a lot of it is just pure memorization.
http://www.answerbunch.com/Answer/25/Improving-Vocabulary-for-GRE
http://www.answerbunch.com/Answer/20/GRE-Preparation-Experience
Hi,
I created a little write-up about my experience in preparing for GRE, especially the English part. It has the books and other resources that helped me.
Hopefully it will help someone.
http://www.answerbunch.com/Answer/20/GRE-Preparation-Experience