This is Ubuntu Gnome. I'm currently Using Ubuntu 14.04 with Gnome 3.10, but afaik it works on Ubuntu 13.x and GNOME 3.x.

Not sure about the Unity interface as I have limited experience with it.

FWIW that F11 transition works the same for me on KDE (4.12.3) on Kubuntu 13.10 - it's been there for quite a time.

I'm using Firefox with the borders set off right now. This gives me a window with no external chrome (no border, no titlebar, no buttons, no scroll area) but set with the standard KDE application bar (which I keep at the bottom a la Win95).

Indeed before Firefox ditched the menubar I used an app to get the same effect pinching a lot of real-estate back (titlebar, menubar, buttonbar). It's interesting that things have moved this way, though not surprising.

Chrome on Elementary OS (Probably consider this Ubuntu 12.04 for this purpose) does a completely chromeless fullscreen on F11 too. Out of interest does OS X support fullscreen on all apps automatically or does the button (it's a window control right?) only show up for supported apps?

Fullscreen mode has been a standard feature of Linux window managers for a long time - it was certainly available in the metacity WM (used by Gnome 2) 10 years ago.