Dmaae,
I purchased Jeff's book because there is a section that explains how you know if you got the hard testlets. The conclusion I came to was that they aren't necessarily "harder" just wordier. I didn't notice it much in FAR, but I did in AUD and REG. For example, my second and third REG testlets weren't necessarily more difficult, they just weren't as straight forward as the first. It took a little longer for me to read through the questions, and what I noticed more than that was that the potential answers were also a lot longer. Just my two cents. I wouldn't worry about it too much. You can psyche yourself out trying to analyze if they were more/less difficult.
AUD-73,79; BEC-69,82; FAR-77; REG-83 DONE!