I'd say REG felt as being the most difficult exam for me (maybe the Regulation & business law parts bear the blame for that feeling). REG time constraint was horrible too.

FAR comes in 2nd place: it was a difficult exam due to the sheer amount of information to memorize (ouch, all that Gvrmtal & NFP Accounting).

Auditing requires structure and understanding (if you understand WHY you need to issue this or that report, then it will be a breeze).

BEC felt easy, 'cause I love the "out of the box" thinking, as the previous poster Watswidme said. I could solve a BEC problem in several ways, and that's why I liked BEC. You can feel free during BEC exam: no time constraints or stupid memorizations required.