Top bar for introducing new features

Both the New York Times and Twitter display a top bar that prompts users to discover new features (click to see images full-sized):

I would be interested to see eye-tracking data to understand  how quickly users notice this type of display. The New York  Times uses a drop-shadow treatment at the bottom of the bar, which visually brings the top bar  forward on the page. Twitter uses a slight embossing treatment and has plenty of empty space around the bar. Both treatments probably aid discoverability.

Twitter uses what I think is a subtle but effective display to indicate when the "Election 2008" bar is minimized:

After clicking the "No thanks" link on the New York Times top bar, I couldn’t find a way to re-display it—and wasn’t sure where else I could look to if I was interested learning more at a later time.