I've got a dual-boot AMD64 system that boots both i386 and x86_64 partitions. /boot/grub is mounted from one partition to the other so that kernel updates for either OS update a common grub configuration. When updating the kernel, it's confusing which entry is for which partition. It would be desirable to include more information in the grub entry's title string to identify which partition is being booted, such as the release (eg. FC4) and the architecture (eg. x86_64). This might be controlled by the same sysconfig file proposed in bug 166954.
A shared /boot is really not something that's expected to work.