[derefr]

I wish OSX had "picture in picture" in a more literal sense: the ability to make a Space (including a Desktop space) into a window, and then move/resize it around on another Desktop space as if it were a Screen Sharing client window.

Though, really, they could go even further: I use Fast User Switching to basically be two people: "home" me, and "work" me, who each use the same apps but logged into different accounts. (The OS manages this far better than the one-off multi-account features of apps do, I find.) But Fast User Switching isn't very convenient when you "are" both users. How about letting me intermingle the Spaces from two login sessions, so I can have a "Picture In Picture" Space from my own other account open on my desktop?

(If you're wondering, Screen Sharing doesn't allow you to connect to localhost. Even if you hack around that [which requires patching some bytes in a private framework], it's still a cruddy experience, especially concerning screen locking and display resolution. And, obviously, slow.)