ShutdownPE was never updated to work with Windows 8/10, so I would not recommend using it.
Not true. ShutdownPE was updated for Win 8.1. the latest release is 1.5.x and was posted back in Jan of 2015 script version is .17
I do not know why chrisR continued to use the old 1.4.x version. He never reported any issues on the 1.5 beta. as far as I am aware there are no outstanding issues with 1.5.x
as far as I remember ShutdownPE was created to be sure hd was first flush than shutdown. And a nice menu for shutdown.
( Later more integrated ...)
ShutdownPE was originally written for and was the fist GUI for Win7PE. Before shutdownPE the only way to shutdown/reboot was to create shortcuts directly to winpeutil.exe and there was no way to eject CD's
ShutdownPE fulfilled this need and added the additional safety of flushing file-buffers and the option to run additional programs before shutdown (ie unmount, save logs, etc)
a bit later if added integration into the start menu shutdown/reboot options (which were previously non-functional) so the start menu was usable and had the benefit of flushing buffers, running scripts, ejecting cd's etc.