Switching windows using Alt-Tab causes the screen to flicker. Additionally, the background rectangle behind the window list appears to not be an rgba window, as you can't see through it like in cube mode.
Fixed in the package, but not built because of freeze.
Turns out this was not a complete fix. There is still a flicker when you release alt-tab.
Should be fixed now (but still not built, so I'll leave the bug open).
Fixed, provided releng moves the package.