On a large campaign we have seen CTR increase by 20% (e.g 5% goes to 6% - not actual numbers). The conversion has remained constant too. One downside is the ave CPC is now 10% higher.
On another campaign it's all over the place (when it used to be stable), O.K. this campaign only gets a small number of clicks a day (~100) but it's either up or down by as much as 50%!
It might be a bit early to say for sure but I think larger headings are something I'd like to see stay.
A lot of Christmas campaigns are winding-down, and that could be enough to account for it.
I had a bit of difficulty getting impressions for a couple of days after the change, but everything back to normal now.
No issue with landing page quality here, as I send traffic directly to a very large online retailer that Google probably can't afford to lose. Plus, the landing pages ARE, in fact, very professional, highly relevant to the ads, and go into a great depth of information.
