I'm beginning to miss Marissa Mayer's axe on things on the main search page. I think Google's primary advantage for a while now has been cleanliness of results (as the difference in relevance between search engines has slimmed); they're opening themselves up to a competitor with a better design/flow by continuing to cram these "useful" items in.
This has been Snap.com 's competitive advantage for years. I suppose Google gave them enough of a head start for them to make something of it if they were going to. Theirs is certainly more mature though. And they have a JS include you can place on your site to enable this sort of image preview on all external links.<p>Theirs customizes the preview type depending on the content. For example, links to stock information shows a little quote and graph preview.
I installed an extension on Safari called Apperture or something - when you select any text it lets you bring up search results in a little sub-window, conveniently organized to put wikipedia at the top and videos in a separate tab and stuff. Search technology is changing, Google are no.1 at the moment but they need to be a moving target.
It was enabled for me by default, and to be honest I didn't care for it at first. It's grown on me a little bit, but I'm still not sure I'll keep it.<p>I highlight while I'm reading, and it plays against that by distracting me with the popup. The article says that it comes up from pressing the icon, but it also includes the text. I'm leaving it enabled though to see if I benefit from it like I do Instant.<p>That said, I'm still unsure about Google Instant because I'll see my result then keep typing and fly by it having to backtrack and see where Google gave it to me.
Interesting implementation detail: the images are XHR'd in with a json wrapped data URI. Try to right click on an image and share it.<p>Other notable notes: they don't render flash in the previews and they let the hovers cover up the right-hand ads.