I wholeheartedly would recommend Princeton Review or Kaplan. Being intimidated or "psyched out" by the test is perhaps the BEST reason to take such courses. You will learn skills and approaches that can be highly effective, if only you will give them a considerable amount of practice (doing the extra homework for these courses is really essential) and ask whenever you have problems or questions regarding the strategies.

I also have one additional caution: you cannot view the GRE as an IQ test. It is not. IQ tests can only be considered accurate insofar as they rigorously and consistently provide a set of results regarding innate intelligence. In contract, the GRE tests learnable skills which graduate programs use as a standard (and "rough") marker for academic aptitude. The clearest proof of this is found in the fact that the test is susceptible to training. A sufficiently practiced graduate of the Kaplan or Princeton Review course will do better than when he/she began training just a few weeks earlier. That means that what you are learning is a skill, and not an IQ. A bad result is not an indication of your stupidity any more than a good result shows your genius.

The only thing a good result will provide is a better chance of getting into a graduate program. That's why you should take such a GRE course, but also why you should focus on things outside the test as well.