about my preparation:
like it has been said for an infinite number of times OG is the best preparation material. i finished nearly 80 % of the questions in the OG for every section.
Also the Quantitative problems(particularly perm-comb and probab. questions) posted on this forum are excellent. I found them a big help in my preparation.
I found kaplan
good for SC and Quantitative.
my powerprep(taken before the OG) scores were 670 and 750.
tests are good in the sense that they keep you grounded :) . my scores in them ranged from 560 to 630.
Good luck to all you guys who are going to take the test!