most features of my laptop don't work reliably (MSI GS65) if I don't use the acpi_osi line, why would that be in that case ? I'm on archlinux with pretty much always the latest kernel
What argument are you providing? In some cases if you pretend to be an older version of Windows then things will work better, since it's possible for the kernel to end up pretending to be a new version of Windows without all the relevant semantic changes in the drivers having been made.
Ok. It should make literally zero difference in that case. What problems do you see without it, and could you mail me dmesg for both cases? (mjgarrett59@googlemail.com)