I'm 35 and applying for Executive MBA programs, so GMAT is less important...hell, some of them only want a 500 and even the big schools are willing to fudge lack of a BA if you have "exceptional work experience" (meaning, lots of cash), so the 640 I got Saturday is good enough.
I used Kaplan briefly and...GMAT for Dummies
GFD is great if you need to brush up on geometry, etc. It's been a while and GFD has the best section I found on explaining math, grammar, etc. Kaplan was completely worthless and the Powerprep free tests were far more useful. I didn't try Princeton.
The essays were far more insipid than anything in the prep books. Like almost embarassingly dumb. They were pretty easy to write, though - I went in with a "five paragraph format" in my head and that's basically what I used.
The quant section was a bit harder. All the prep book tests try to give you "one of every type" of question and don't repeat question types much. In the real test, however, I got 3 combination/permutation questions, which was probably my downfall, as I didn't really study those much. On the other hand, I got lots of geometry, which I love, so I made up for it. Man, I have crammed so much geometry info into my head over the last month...and sadly, six months from now I'll have forgotten how to compute the surface area of a cylinder and those Pythagorean triplets. (Well, except that I'm sure I'll be using all that info in my management career <cough>)
The verbal was hilarious. By sheer coincidence, I had a personal interest in all three topics, so I enjoyed reading them. I got to the last question with 22 minutes left, and I wasn't really hurrying. Apparently I'd hit the ultimate hard end of the CAT hard/easy tree (I ended up at 94th percentile in verbal) and the CAT through me its toughest question at the end. What a monstrosity! Half a dozen prepositional phrases, a semi-colon, a full colon, all kinds of stupid punctuation and weird tenses, in one mammoth paragraph-long sentence - I mean, no one would really talk like that! I burned 20 minutes on the *last* question alone, mainly because I had them and what the hell...of course, I'll never know if I got it right or not.
I was a little ticked that I'd spent time looking up GMAT codes (the four-digit school codes) so I'd be ready...and then found out you pick them by name on the computer screen. Jerks. And then at the end, after you've finished, you have to sit through all those stupid demographics before you see your score. Jerks.
Finally, Sylvan needs to get with the ergonomic program. Their keyboards were cheap junk (loved that during the essay!) and my carpal tunnels were on fire during the long hour of typing. Oh well...I'm done.