Nexus 7 Screen Capture Does Not Work. It Actually Does.

Symptom:

I have learned that you can do Volume-Down plus Power simultaneous button press to capture the screen as a part of the Jellybean feature.

I tried this many times and it did not work. Only thing I saw coming up was the volume control.

Resolution:

The buttons work as advertised. I was not doing this right (as with a several other people posted this complaint). I was thinking that by pressing these buttons the screen shot starts right away. And that's where I was wrong.

The real trick is this.

• Press the power and volume down button simultaneously and hold both buttons pressed for 1-2 seconds (and be patient) until the screen capture completes.
  
• Note that if the volume thing comes up on the screen you messed up the timing of simultaneous pressing. Release both fingers and try again.
  
• You could also be inadvertently pressing both Volume Up and Down simultaneously as you do this. Try holding the volume button really towards one edge. (Never use your thumb ;-) 
  
• Do you have a teenager handy? Ask him or her try it. If it works with them, then, well, the machine is fine.
  
  Good luck!