When one tries to shutdown a OLPC XO-1 via the normal halt command one will get a bit of weirdness. No idea what exactly happens, but the device doesn't fully shutdown, but instead gets into a weird mode where the power LED is still on, but the machine no longer reacts properl. No idea if this state is good for anything or just a bug.
Anyway when one actually wants to shutdown the XO-1 properly, one simply can do it the same way as the Sugar GUI does it, by sending dbus message to the power managment, which the following command will do:
The XO-1 then shuts down as normal and is properly 'off' once done.