Alternate (keyboard) task switching method for CM9
My 3.2 method does work with CM9, and the default launcher (Trebuchet), with these adjustments:


Go to Settings->Launcher->Homescreen->Search Bar, and remove it.  Keyboard focus will default to the apps button (the ::: icon) at the top right
Arrange icons on the right side of the screen instead of on the left.  Down-arrow, from the apps button, will go to the top-right icon in the same way as it used to go down to the top-left from the search bar in 3.2


Other launchers are also an option (Go Launcher EX duplicated the old behavior, although it forces phone UI elements), but this is the shortest path if you're otherwise content with Trebuchet.