How many keywords are you using per each Ad Group? Did any of you see an improvement once you reduced the number of the keywords in each a group? Thanks!
We've found that it is best having one keyword per ad group for your very best keywords, 5-10 for your ordinary keywords, and dozens for poor performing keywords. Lumping them all in together could mean that the average performance has a negative effect on your best keywords. Having fewer keywords per ad group means you should find it easier making ads that suit the keyword.
You shouldn't group keywords together based on their performance. Keywords should be grouped together in such a way that you can write a single advert for them and still make it relevant (and ideally include the search term). If you are breaking up large Adgroups into smaller ones so that the advert text is more relevant, then you should get better clickthrough rates, and hence a better Quality Score. If you break up large Adgroups into smaller ones for no other reason that you don't want a lot of words in an Adgroup, you'll probably see no benefit. And in addition, it'll take longer to test new adverts, as each advert will be getting less data. It doesn't make sense to break up Adgroups without a clear justification in terms of advert-writing.
There's no point in having more than 50 words in a content-targeted Adgroup, as Google only looks at the first 50 entered...