frankleeceo - 4:57 pm on Oct 19, 2013 (gmt 0)
I do notice that when I first slapped on async codes it, the reporting pageview out of whack for a few days which brought down ecpm (eCPM is calcualted by pageviews and earning). But that hiccup is corrected within about 1 week where the pageviews are reported again correctly.
It counted 10k pv's as 60k~80k or some insane amount. So for a few days I got reports of 5 times my normal pv. But I thought it was OK because the monetary amount didn't change much so I disregarded this as a simple reporting error on Google's side.
I did make more money overall after switching to async code. My site layout called for adsense codes in widget area which does indeed slow down content whenever the ad server slows down or breaks.
I have replaced all of my adsense codes into async whenever they load "before" content. It improves the usage and load from an UX point of view.
It probably won't help you if all of your adsense codes load after content.