Math can be easily mastered to tell the truth. (i score around 630)
For me Writing is a different story and CR a bit also.
Hardest for me is the writing corrections.
Essay isnt too hard, but for correcting errors, if its not obvious, i usually don't catch it.
right now I only have about a 500 in it.
critical reading is just a matter of timing, i still need improving and i plan to read good newspapers like The Inquirer which sat section do you find most difficult?