I am in the final weeks of a TestMasters class right now, and I definitely do not regret my decision to take the class. My teacher is great and the homework books are extremely helpful -- it is very easy to pinpoint you weaknesses, as the homework questions are broken down by question type. So far, I have gone from a 160 on diagnostic 1, a 166 on diagnostic 2, and a 167 on diagnostic 3 (one week later), and feel that I still have a great amount of room for improvement. I am not taking the exam until October and I will review the questions that I got wrong in the TM homework for the rest of the summer and take self-administered diagnostics. In any case, I feel I am far more prepared to self-study for this exam now that I am scoring where I am . . . I know my weak spots, and I know to improve them, thanks to TestMasters. I just need to practice.
Warning, though: A friend who started off in my Pittsburgh class just transferred to a class in CT (had to move because of an internship) and has told me his new instructor is considerably worse than the one who teaches the Pittsburgh class. Even so, I recommend TM, as the materials are top notch.