Please post your reviews if you have used Adsense 970x90, 300x600 ad sizes on your site(s). I've used 300x600 few months back on all pages but had very poor CTR and even CPC. So, replaced it back with 160x600 and 336x280 on most pages. Most of the time 300x600 fills in with 160x600 (centered) Yet to try 970x90 ad size as replacement for 728x90