I got myself into a bit of an adventure with my office PC, recently upgraded to Mint 11 (Katya), and I'd better take some notes before I forget and have to relive the adventure.
As installed, Alt-Tab popped up a panel with thumbnails of all open windows, and let me cycle among them in a rather static way. (Choice of the word "static" relates to what follows.) In past versions, I've had Mint set up to task-switch with a bit more flair: displaying a rotating list of snapshots of the app windows in a horizontal bar, three at a time, with the center one brought to the foreground behind the switcher, and cycling through the list (ring) each time I hit Tab while holding down Alt. Bear with me if I don't use the official terminology for this effect, because part of today's adventure was learning some terminology that I do not find entirely intuitive. All I remembered going in was that (a) Alt-Tab was the key combination to make it happen (the same one used for "cool tabbing" in Windows, and thus easy to remember), (b) it required Compiz (installed by default with Mint), and (c) it was not a default behavior and thus needed to be set.
So I went to the Control Center, thence to CompizConfig Settings Manager, and stared at a multitude of choices, not many of which are self-explanatory. In tweaking settings, I managed to cause the maximize/minimize/close buttons on all windows to disappear (not desired -- I really use those a lot). I also found a setting labeled "Compiz Fusion Icon" (in Control Center > Hardware). It seemed odd that there would be a setting for an icon (doing what? choosing which version of the icon to display?), so I clicked it a couple of times but observed no results (because I'm unobservant ... more about this in a second). Finally, somewhere in the process of mucking with settings and dealing with messages about conflicts over certain key-combinations (most notably Alt-Tab and Shift-Alt-Tab) I managed to disable Alt-Tab entirely.
So I'll note here the key information necessary to resolve all this, since I'm sure I'll forget it by tomorrow. First, the "Compiz Fusion Icon" button in Control Center > Hardware actually did something: it added a "Compiz Fusion" icon to the GNOME panel (in fact, one per click, so I ended up with two side by side). Right-clicking the icon lets you switch between Compiz and Metacity, and gives easy access to the Compiz settings in the Control Center. I suppose the icon is handy if you plan to switch between Compiz and Metacity regularly; I don't, so I banished the icon again.
Second, to get the desired Alt-Tab variant, I needed to deselect "Static Application Switcher" in CompizConfig > Window Management and select "Application Switcher" instead, then modify key combinations as desired. (In point of fact, I ended up opting for the fanciest switcher, the "Shift Switcher", once I read about the choices.) Having very limited memory, I decided to change the keys for "Shift Switcher" so that Alt-Tab and Shift-Alt-Tab rotate forward/backward among windows in the current workspace, and Super-Tab and Shift-Super-Tab do the same in all workspaces. (Now if I can just remember that second part ...)
Third, the missing maximize/minimize/close controls for the windows were the result of the "Window Decoration" option under CompizConfig > Effects being deselected. (I don't think I did that, but it's possible an errant click was the culprit. I've seen one or two forum messages suggesting that it might be the action of a gremlin.) Here's a prime example of what I mean by unintuitive terminology. To me, calling those controls a decoration is like calling a door know a decoration. They're controls! I think of "decorations" as being not particularly functional, which those controls are. For that matter, I don't find them all that decorative. Anyway, turning "Window Decoration" back on restored the controls to their normal positions (and my blood pressure to its normal level).