This has been a hell of a Lion day, and I’m barely catching up with the flow of articles, tips, and Twitter chatter. I was skimming Shawn Blanc’s Lion review and this bit got my attention: 

PLUG AND PLAY WITH AN EXTERNAL MONITOR

I adore the way Lion manages laptops and external monitors. I find it much more user-friendly than the way previous versions of OS X have managed it.

The tried-and-true behavior of how OS X deals with a laptop and an external monitor has been this:

• With the laptop lid closed and the computer asleep: Plug an external display, wake the computer, and the external display will be the only working display. If you were to then open your laptop lid while an external display is running, the laptop’s screen stays off.

• With the laptop lid open and the computer awake: Plug an external display in and you have two working screens. If you were to then close your laptop lid, the computer would go to sleep.

In Lion, this behavior has been greatly improved:

• With the laptop lid closed and the computer asleep: Plug an external display in, wake the computer, and the external display will be the only working display. If you were to then open your laptop lid, the laptop’s screen would turn on and you have two working monitors.

• With the laptop lid open and the computer awake: Plug an external display in and you have two working screens. If you were to then close your laptop lid, the laptop’s screen turns off and the external monitor becomes the only working monitor.

In short, opening and closing your laptop’s lid is like adding or removing a second display, and does not affect putting the computer to sleep.

I’ve always found the old behaviour annoying, and I agree with Blanc — it’s a welcome change.