This is the first algo change that his hit one of my sites big since 1997. My main site lost 30-40% of traffic. I fell from #1 to #6 or #7 to some big keywords.
The site has two adsense blocks above the fold. 728x15 link bar and 336x280 large box. It also has almost all the content above the fold. Most users don't have to scroll down at all.
I've long thought that the 728x15 unit was a bit spammy, bit it was hard to argue with the revenue that it brought in. If that traffic comes back without it, it isn't worth having.