Whoops, sorry for the delayed reply... I'm behind the eight-ball with things due in the next couple of weeks. My life is a deluge of journal articles with things I highlighted at 3 am!
I had taken the GRE twice in the dark days of the paper-and-pencil, analytical-is-a-full-section era. The first time, I had a mid-600s in V, and mid-500s in Q. The second time, mid-500s in V, and low-600s in Q. That was '98/'99. I had prepared on my own, getting books from Barnes and Noble (I think it was one Princeton Review book and one Kaplan book). And not that it matters, but my A score was stable around 620.
Last summer ('07), after taking the Princeton Review course, I had a 730V, 720Q, 5.5 AWA. From my own distorted view, using my SAT score as a guide, I overperformed in Quant (670 SAT) and underperformed in Verbal (770 SAT). I never took an SAT course, though, so obviously there are a lot of caveats. Also keep in mind that I have a completely unrealistic yardstick that I use to compare my standardized test scores to... my wife, who got a 176 on the LSAT (out of 180... 99.9xx percentile). She's the smart one in the relationship
What specifically did the Princeton Review course do for me? One, I generally suck in math, GRE score notwithstanding. I didn't know/forgot everything about geometry, especially triangles, and was crap when it came to exponents. As disgusting as it is for someone who has already completed grad classes in multivariate statistics, I was screwing up probability questions. They got me up to speed.
Two, time management and general test strategy. The first ten questions on each section really are critical, and I had to train myself not to panic when I took the lion's share of my time on those first ten questions for Quant. (Verbal, not so much... I took as much time as I felt I needed, and it worked out. My vocabulary is decently extensive, and I read somewhat quickly).
Three, and this was critical for me, I had one free one-on-one session included with my course. I was able to address a key problem I was having: neatness. Yeah, neatness. When it came to working out the Quant problems, I'd freak out, and write randomly all over the page. This lack of structure caused numerous careless errors.
I would not have been able to get a 1450 without this class.