I benefited by getting a better idea of the language used in the real exam questions. As diligently as test-prep companies like to try to emulate the PCAT, the wording, length, tone, and content of questions don't always match the real PCAT. That is, some questions may be worded too difficultly or easily.
The difficulty of the practice exam was about the same as the real thing except that the expanded number of questions on the real thing will make the test more difficult to complete simply because you are in a greater rush.