To add a suggestion that can be included very quickly and easily and may well be sufficient to unexperienced user:
#5: Change the help text from the tickbox when asked where to install grub:
It should recommend unexperienced users to keep the default setting rather than mislead users "to install GRUB to all of them" (Drives a meant but this could easily be misinterpreted to partitions as well). The note at the bottom on partition boot records should be changed to a clear warning that other OSs may not be able to boot if Grub is installed to their boot partition record. I would suggest someting like "In dual or multi boot installations make sure to NOT install Grub to your Windows or other OSs boot partition".
To add a suggestion that can be included very quickly and easily and may well be sufficient to unexperienced user:
#5: Change the help text from the tickbox when asked where to install grub:
It should recommend unexperienced users to keep the default setting rather than mislead users "to install GRUB to all of them" (Drives a meant but this could easily be misinterpreted to partitions as well). The note at the bottom on partition boot records should be changed to a clear warning that other OSs may not be able to boot if Grub is installed to their boot partition record. I would suggest someting like "In dual or multi boot installations make sure to NOT install Grub to your Windows or other OSs boot partition".