Well, it's a solid extension that does what it says on the tin - unfortunately it's no longer enough, apparently. For example I tried to use it to enable previews of Twitter pages in pinboard.in's organize mode - and sure, the view itself loads, but it's broken, because other requests and scripts fail in ways I'm not motivated enough to investigate.

The web has changed. The header itself is incredibly useful - click jacking was a scourge, and sometimes really is. But the approach has its downsides.