If you ask me, I think its already kinda late to think about GRE if you're applying for Grad schools starting Fall 2007. From what I have found out , most schools have their application deadlines as early as second week of December (although lot of them don't have it until late December or even early January). The latest that you could take the GRE, inorder to have your scores in before the deadlines, would be around second week of December (and I personally think thats pushing things a little too far). The scores reports take about 2-3 weeks, after you've taken the exam, to get mailed to the schools. So if u are serious about applying and confident that you can prepare within few weeks, then you should register for the test asap. As for the prep materials, I don't think any GRE books or any other preparation course guarantee you an extraordinary score. You can practice from any book as long as the practice exercises and sample exams in there reflect the current format for the test. The format for GRE and any other standardized test changes regularly (the format for GRE is changing from 2007). So make sure you're familiar with what the test is going to look like. Like someone mentioned in one of the replies, GRE measures your aptitude. It shouldn't matter how much time you spend practicing (I may be wrong). But if you think you're weak in some area thats being tested, you should put some extra effort in preparing for that section. Otherwise you should be fine.