Comment 39 for bug 543294

Wow, thank you Minsang Kim! That actually works 100% perfectly for me! :)
I also want to add, if you still want plymouth to show, it also works with:

GRUB_CMDLINE_LINUX="quiet splash acpi_backlight=vendor"

So you don't need to remove the default options, just add the last. Thanks again for workaround!