I guess I should put in my 2 cents. I installed these fans for the brutal SoCal summers and traffic last fall, so I haven't had the chance to try them out in summer conditions yet. But I have made a few very un-scientific observations.
First, since the fans only cool the heads, I expected them to have little or no effect on the oil temps. However, my oil temps SEEM to be better controlled. The oil temps had topped 290 degrees last summer, but since installing the WPW fans, my oil temp has not exceeded 250 on a couple 90 degree days this spring. How well they handle 110 degree temps in slow traffic remains to be seen.
When idling after warming up completely and the fans are working, I do think there's a little more heat felt by the rider (or maybe I just notice it more because I'm thinking about it more). I don't feel it on my right leg, but there's a lot more air removing heat from the cylinders, and that larger volume of warmer air can be felt while sitting still. This might even increase rider discomfort in high heat and slow traffic, so if you're thinking about getting these fans for your own comfort, you may be disappointed with the results.
I think these fans help a little with cylinder head temps, but they may actually add to rider discomfort while sitting still. They might be insurance against high heat damaging your heads, but nothing beats a set of pipes and a good tune to increase rider comfort.
Stay safe,
Dan