Rode a century today on the Power Arc
It's pretty similar to the regular Power saddle but it does feel more rounded, provides a smoother ride and I feel it's a little more comfortable. I rode 102 miles today on my race bike and I felt less sore than I would normally do for that distance. Overall, I think it is a decent improvement over the already excellent Power saddle.
I'll be interested to see opinions of the Power Pro Elaston model which also just came out. This other new Power saddle is meant to increase comfort further.