To be more precise, the ALT+Tab works as in Mac (I believe). It switches between windows of the same application. Not between applications themselves. Which I just don't get.
Whenever doing anything I type in Vim in a Terminal, Alt+TAB to another application, and check the output. I am almost never in the same application between an Alt+Tab. It baffles me that this is default behaviour.
GS 3.6 as on Gnome Ubuntu Remix, no extensions
Alt-Tab switches between applications, irrespective of how many windows a given application has open.
Alt-' switches between windows of the currently selected application.
In the screen grab above, I've pressed Alt-Tab and reached the terminal window, then pressed Alt-` and am cycling between the two terminals. In practice you keep your thumb on the Alt and the pinky switches between the tab and ` (back-tick is above the tab on UK keyboard, it might be ~ on US keyboard, my memory fails).