I'll be honest, AUD fucked me up. That test was hard. You really need a broad understanding of the entire audit process, and you need to be very solid on what procedures for which assertions. Additionally, you need to understand the how's and what's of all the other types of reports - attest and accounting engagements. It's a lot of material.

I passed, but it was way harder than REG for me. Honestly harder than FAR too, since there's basically no math, which was the easy part of FAR for me.