Wow. Maybe. I never thought it might be just my Mac. I use an Apple keyboard. I can activate app switcher no problem. Just that the full screen app isn't there.
For example, watching a YouTube video in safari in full screen mode. I can Com Tab to another app, but when I try and Com Tab back to Safari, the non full screen YouTube page is all black and white without a playing video and to get back to the fullscreen video I need to go to Mission Control and choose the space with the video. Maybe a Spaces issue?
I am using Total Spaces instead of Mission Control (which is not disabled, just barely used), but I know of that YouTube "issue".
When I use Safari in not fullscreen mode and watch a YouTube video in fullscreen, that video is put into a separate space/desktop.
I can still CMD+TAB to other applications though and CMD+TAB to Safari brings me to the YouTube video in fullscreen, but if I use my mouse to show all spaces and switch to Safari (not the YouTube fullscreen space), I get that black and white window, but I can still CTRL+TAB or click other tabs and use CMD+TAB to switch to other applications.
CMD+TAB and Safari seems to remember the last active window.
I am running 10.0.3 by the way, with all apps updated to the fullest.
Maybe you can share a screencast of your problem to see if it is a problem or just the normal behavior?