This is what I'm talking about

http://weblogs.mozillazine.org/roc/archives/2006/06/the_future_is_now.html

Nightly webkit builds seem to be able to rotate foreignContent as well, but the rotated content is inactive. The new Mozilla trunk builds seem to keep user interactivity intact.

In other words, this is awesome. :)

Indeed it is! :)
But what's the purpose? :p

To make anything that Gecko can render manipulable at the same level as SVG of course. Take a look at Opera for Nintendo DS sometime - that sort of behavior can be accomplished a little simple Javascript with this support. Or picture Expose-like behavior in your own webpages... it's good stuff.