netmeg - 3:46 pm on Feb 21, 2012 (gmt 0)
Images seem to work well for me.
But Google sends you messages to serve Google. And their "simulated experiments" may well be run on a GROUP of sites, of which your site could be one, and on average the GROUP showed improvement, which doesn't necessarily mean you would. It's hard to imagine Google being able to scale individual simulated experiments, even if they just picked sites above a certain threshold of traffic.
I'm all for testing, and I'm always doing it. But I treat all the helpful hints in my AdSense dashboard with skepticism.