What's been your experience working with select ad extensions like Sitelinks, Review Extensions and Callout Extensions?
Confusingly, I haven't seen ad extensions work very well at all. You'd think "more real estate is better!" However, except for the most generic, high-funnel, or brand terms, things like Sitelinks tend to give shoppers the opportunity to get off-track, hurting conversions. For example, if you're looking for a Canon T5 camera, and I have an ad for it, but it carries Sitelinks to "Canon Cameras" and "DSLRs", then if you click on those, I've actually moved you UP the funnel--which is the exact opposite of what I want to do. Testing is the key to success here, though, because if you searched for "electronics stores", then having a top-level category breakout in your Sitelinks could work very well, as it takes a generic search one step more specific. You see sibling considerations for the other types of extensions, but they're all similarly testable.
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Up and to the right!