First time I took My Gmat preparing on my own and got a score of 630.
I then took the Princeton course , and got a 710 on the GMAT.
PR's learning method is very effective especially for those like most of us who like to solve quants in conventional methods. whereas our regular methods are time consuming, with PR training one can beat the time easily. I got a 50 in quants with 5 mins in hand. For Verbals we have good training in your most weakest concerns. and the Time pacing technique taught at PR is excellent teaching you where to spend time and gain high score.
The online practice test is very helpful. you have over 10 free complete tests and plenty of drills. With this it is impossible for u to go to the test hall and be worried for a minute.