I remember the first time with Power Hour. When I picked up my weights, I made sure to go a little lighter than Cathe, and was very surprised when she did biceps (or is it tricps) with 15#. I thought "that will be way to light". HA!
I personally find endurance work like this much more challenging for me than heavy weight work.
I didn't even do the lunge section the first time through. It took me a few times to work up to doing the whole thing (and then, still with some longer pauses than Cathe has!).
But I've learned to love workouts that I have a hard time getting through the first time. It gives me something to work up to (and after a while, I was able to do heavier weights than Cathe uses on most of the exercises! Of course, if I went back to it now, since I haven't been doing endurance work as much, I'd probably drop down again.