I've added a "Show Next Result" button to the search page. This moves the preview forward to the next link in the results, and if you're at the end of a results page, it fetches the next one. The beauty of this is that you can go through links very quickly without having to hunt through the results page.
I was also hoping to get the up and down keys to also cycle through results, but this looks like a cross-browser minefield. I had it working in Safari, but only after you manually set the focus by clicking in the window, I couldn't get it working with Firefox, and I haven't even looked at IE yet!
Another addition I want is some indication of which link is being previewed. I'm thinking about setting the table border of the snippet below the result to 1, so you get a selection box.
One disturbing thing I noticed while testing my latest changes on the PC is that youtube links in the results seem to hang IE when they're previewed. This seems to be new, I'm worried there's been some flash changes, and it might affect a lot of sites. Firefox and Safari still seem fine, but I'll be trying to work out what's happening tomorrow. It's filed as Previewing YouTube sites hangs IE.