Avoid USML-SLEAZY, the questions aren't very represntative of step one, and I was definitely getting 15-20% more questions right on sleasy vs. Qbank. I got it free for a month last year when i took the boards, so i used to switch things up a bit, but I'd never pay for it. I did enjoy Q-bank though. The NBME assessment is definitely worth the money, a good predictor of your actual score, and good practice for pacing the exam.