Compared to all the other study resources, the opted practice test is the most accurate as far as degree of difficulty goes. Some areas were way off for me, others were right on. For example, I got a 400 on RC on the opted one, but a 300 on the real thing. But for physics I got a 360 on both. Overall, I got a 360 on the opted one and a 350 on the real thing, so I guess overall it's a little easier, but not by much.
Good luck!