I have had exactly the same problem on my Acer V5-571G: the laptop shuts down, turns off its power LED, and then starts again after a few seconds. It occurs more often when working on battery.
The problem seems to arise from incorrect work of pm-utils. But if you write
/sys/bus/*/devices/*/power/control, the kernel takes control over power management at the specified devices - and somehow this makes the hardware to shut down correctly.
So I have written a script:
case "$1" in
stop) for i in /sys/bus/*/devices/*/power/control ; do echo on > $i ; done
and to make it being executed every time before shutdown I've placed it under name K32power-control-on into /etc/rc0.d directory (don't forget to make the script executable, sudo chmod +x K32power-control-on). After that the laptop shuts down ok.
I think that there are only a few buses/devices which need to have 'on' value written to their power/control, so the list of devices in the script can be restricted, but I just didn't investigate further.
UPD: Here is a more refined solution of the same problem: http://www.pbehnke.com/main/node/11