I'm sorry for the off-topic but I can't help it with that blog design: is -webkit-transform: rotate() the new <marquee> tag? The Panic team creates great products with fantastic designs, but I find this choice a bit motion-sickness-inducing.

Back on-topic: it's great that Safari is now offering an official way to have extensions. I had tried at one point to write a plug-in for Safari and soon realized that the existing ones (e.g. 1Password, Evernote) relied on "hacks" and work-arounds. Let's just hope the extensions are as easy to develop as for other browsers, like Chrome. (with which I recently dabbled with)