Here is how to solve this:
- Open CompizConfig Settings Manager
- Go to the Unity Plugin settings and deactivate (uncheck enbabled) for the Alt+Tab and Alt+Tab+Shift shortcuts (or even all the other "switcher" related shortcuts.
- Then go to the CompizConfig main menu and to the "Window Management" section and enable one of the "Switchers", for example "Shift Switcher" or "Static Application Switcher".
All of these Switchers expose the old behaviour.
If you don't mind using the mouse instead of keyboard-shortcuts - one more note:
The Unity Launcher (the menu that comes up when you go to the left side of the screen) also works like an "old" taskbar. Clicking on an active app's icon brings that app's window to front. If an app icon indicates two or more windows of one app open, double-clicking opens a multiple-window grid that I think is more convenient than the multi-window "sub selector" that comes up through Alt+Tab for that same app group.
Actually now, I've come to accept the "grouping switcher" but with one novel way of using it (novel, at least for me):
I've found out that once you're working in one window from a group, you can switch between windows from this group by using ALT+^ (instead of ALT+TAB), for example switching between multiple instances of leafpad. And switching between windows from one group is what I usually do most, or wanted to do with ALT+TAB before. So this as a tip for everyone not knowing this very handy short-cut.