I've played with a display unit a few times at my local Verizon Wireless. They do have a little bit of give, but there may be some devices where there's more or less of it than some others. If you really want to be sure and you have a remotely nice camera with decent auto-focus, try getting an example on video and posting it on YouTube for the rest of us.
Just took a close look at mine. It looks like they are actually two rocker buttons. Never noticed this before.
Yes there is some play. The top of the buttons is basicaly flush with the lower plane of the phone but they set above the screen about a mm or so. That is where I see play. When I push them toward the screen they rock forward till they hit the glass.