moving or repositioning an iMac

I have a new iMac 21.5". How sensitive is its hard drive to vibration and/or movement? Is it ok to adjust screen tilt, or adjust viewing angle by rotating the computer slightly while it is on?

The "everything Mac" manual warns against repositioning it while it is on.

I do it all the time. It's fine. As long as you aren't moving it like there is a 5.0 magnitude earthquake it should be fine.

And doubt the manual is referring to adjusting the tilt/angle of the screen - more of a moving the screen to a new location where you're physically picking it up and moving it about.