The AAMC practice tests were great for the money, great supplement to the Examkrackers I used. They give a pretty good idea of the level of questioning for the real test. Since the EK questions were usually harder/more specific than the real test, the AAMC materials were good comparison.
If you sit in one place for eight hours and take the test according to how it's supposed to be taken, they will help a lot. I spent a few full days at my library looking like an idiot. It made me a lot less nervous on test day, though, especially when I finished early on sections.