All of USMLERx's questions are written by medical students that have already passed Step 1 (such as myself). They're then peer-reviewed and professionally reviewed 3 or 4 times before going live.
As a disclaimer, I am getting paid for the questions I'm reviewing/writing but I hardly think I'm breaching medical ethics here by recommending it as a resource....
I don't get paid to recruit people....
As I mentioned in my previous posts it's got a few problems but I think it's a fine resource. Having gone through Qbank 100% and comparing the two I think USMLERx does a good job of filling in the gaps that Qbank leaves.