The new default adsense fonts will not necessarily increase your CTR. For my website, as soon as the new fonts were implemented, I saw a decrease in CTR and earnings. The reason for that is that if your ads don’t blend nicely with the theme of your website, people will not click on the ads. On my website, I use Arial with 12px font size. However the adsense ads were in Verdana at 14px font size. So they were sticking out like a sore thumb and looked more like ads than blend in with the content of the website. Result – decreased CTR and earnings. I’ve changed it back to what it was before – Arial at 12px and I’m hoping everything will get back to normal now.