I shut down my new MBP, and the little light on the front of the computer stays on. Why does that happen?

Intel portable macs hibernate, which is new for macs.

When you close the lid or select apple->sleep, it turns off the backlight and turns on the white light sold. You may still hear the HD or fan. At this moment it is "paging to disk", in other words it is preparing for hibernation. Depending on how much memory is in your mac, it takes anywhere from about 3 to 20 seconds to hibernate. If you were to remove the battery at this time and deprive it of power, it would shut off, and when you restarted it, it would have an 'unclean' restart and would take awhile to boot and would nag you when it got loaded up that you ought not to have done that.

If allowed to hibernate, when it's done, you will hear the HD park and the sleep light will start pulsing - it always starts with a very bright pulse on. If you open the lid or press the power button now it will simply wake from sleep, instantly as always, and the hibernation file is deleted. (it can be quite large, as big as your memory is)

If you remove power while it is hibernated, the power light turns off and it is OFF. You can remove the battery and unplug it for as long as you like. When you restore power and press the power button, it will NOT chime. The backlight will come back on, and a washed-out image of what was on your screen will appear. A progress indicator will appear at the bottom of the screen - it looks a bit like the firmware update progress indicator, or a bit like the windows startup progress. 19 units will light up over the next 4-15 seconds. The picture will be restored to normal looking, and the laptop is now fully awake, as though it had merely been asleep.

Previous powermacs could not hibernate, but had a backup battery and would stay asleep for up to 5 minutes without main battery, this was useful for when switching to a spare battery where AC power is not available. Now with macbooks, as long as you allow it to finish preparing for hibernation (20 sec max) you can remove power for as long as you like and still get the quick wakeup when power is restored. Previous ibooks did not have a backup battery and so you could not change the battery while the ibook was asleep, but the macbook can.

Mac Pros and iMacs cannot hibernate. Although it is much less necessary for them, it would still be a nice feature. I don't know if they have the necessary hardware support to hibernate - I doubt it.

I have seen my macbook pro fail to hibernate on several occasions. I close the lid and the backlight goes out. It may or may not be creating the paging file. The sleep light never starts to pulse. If I put it in my bag and leave, by the time I get where I am going, the laptop is HOT, OFF, and the battery is DEAD. I assume it failed to sleep and has been fully awake in my laptop bag for the last few hours, which would explain its condition. (running with the lid closed, not asleep, eating up the battery and heating up the laptop) So I always wait for the sleep light to start pulsing before I put the laptop in my bag. If it has not gone to sleep within 30 seconds, I reopen the lid (and it is awake, there is no usual delay from waking from sleep, it just turns the backlight back on) and I try to sleep it again. Sometimes it refuses to go to sleep and I just shut it down and put it in the bag and will restart it later. Also since the HD is spinning until it is asleep, it's less safe to move a laptop unless it is sleeping.

Mine is not shutting down all the way either. It sleeps just fine but when I shut down, the power light stays on when I close the lid and it gets warm. To boot I have to hold the power button down for several seconds (at this point when I close the lid the light now stays off - so it is not truly shutdown). Then, when I press the power button momentarily it boots up as expected.

Two possibly related issues:
1. My firewire port is now dead - I had an external hd.
2. I just threw away a quirky power brick that appeared to have a short at the MagSafe connector.

Thanks,
Daren

macbooks follow a specfic routine you can check for when sleeping

1- user closes lid
2- backlight turns off
3- power light turns on solid, at medium brightness
4- macbook writes "safe sleep file", time varies depending on RAM installed, usually 0.5 - 3 seconds (ichat is also logged out)
5- faint click heard as macbook parks hard drive heads after flushing caches to disk
6- sleep light begins pulsing by going from mid to full brightness and starts its pulsing

it sounds like your macbook is failing at step 4, which for this sort of issue, is very common. (never makes it to step 5)

A) I found occasionally when I slept my macbook and put it in my bag, it would never perform step 4 at all, and would continue to operate, with the backlight off. Even making noises when friends went in and out of ichat. This was usually unnoticeable because I'd have stuffed it in my laptop bag by then. If I opened it back up before the battery died, it would wake up and have a low battery and would be HOT, but usable.

B) The other variation I saw was a freeze on step 4, or (A) gone too long since puting it in the bag. When I would pull it out of the bag an hour or two later, it would be HOT, off, and the battery totally dead.

Because of (B) I started a habbit of always waiting for step 6 (sleep light starts pulsing) before placing my laptop in the bag. I have not seen (B) happen in at least a couple months so I assume it was fixed in an update. I still see (A) from time to time and maintain my habit of watching for the sleep light before bagging it. When it fails to sleep, I open it back up and try to sleep it from the menu. This usually just goes ignored, at which point I restart it and when I get back to my desktop I sleep it and it pretty much always works.

Mine seems to be sleeping fine - just not shutting down completely.