I took a diagnostic test with Princeton Chandigarh in July 2015 and scored a 610 (QA 41, VA 26). Initially, I was a bit apprehensive about my decision to join a classroom program as I felt that self-study would be sufficient. However, the classes were very helpful because they pointed out the common mistakes which I had been making all along. Verbal classes by Mukhvinder ma'am and Maths classes by Mukul sir helped me to realize the mistakes. Excellent maths tips and concepts were explained which help you to get into the 49-51 range. You have to take at least 8-9 mock tests to be able to formulate an effective plan for yourself. You get 10-12 full length Princeton mock tests in addition to some other tests in the Princeton package. The exposure to question styles of different tests brings you closer to the real test. When I started scoring in the 690-760 range in the mock tests, I consulted the master trainers Deepti ma'am and Mukhvinder ma'am for the much needed improvement to break past the 700 barrier consistently. Some valuable tips by Deepti ma'am for Maths made me realize that too much stress on the Quant section was hampering my Verbal score. Using those tips, I modified my approach and practiced regularly in the last week before my GMAT.
Overall, it has been a very good and satisfying experience.