How to grab Cmd-Tab on Macintosh instead of sending to Screen Sharing?

If you press optioncommandx, then the screen sharing window will go into 'observe mode', and won't accept any mouse or keyboard input. Then you can press commandtab and switch apps. I know this doesn't really fix your problem, but it's at least a quick workaround...

Realize this is old but I have found that killing the 'RFBEventHelperd' process using the Activity Monitor app allows Command-Tab to work properly with Screen Sharing. I have not seen any side effects in killing this process.

Only issue is that you have to kill this process every time you launch a new instance of Screen Sharing.

Here is the link where I found this solution: http://hints.macworld.com/article.php?story=20120221065822722