Ok, so I finally got the courage to attempt a dualboot with Win8 again. Installation was painless after cleaning up C: and then shrinking the volume to make room for the openSUSE partitions. Everything behaved normally (and exceptionally, bravo on 13.1) until I booted into Windows 8.1 again. Now GRUB is totally gone (as expected). I am using a Sony Vaio Fit 15 with Windows 8.1. I installed openSUSE 13.1 64 bit with UEFI and Secureboot enabled. I am also using btrfs as I intent to experiment with getting Bumblebee to work.

Ideally, I'd like to be able to chainload GRUB from the Windows bootloader so that I won't run into this problem again. I have encountered this problem invariably with Windows 8 on several machines, and am thus unwilling to simply reinstall openSUSE or GRUB. The Vaio uses UEFI and GPT. In this regards EasyBCD does not work with Windows 8.x as it can't handle GPT. Previous installations were rendered inoperative by EasyBCD.

This problem came as I was writing a tutorial on the topic.