I just looked at the boot sector on the 3 machines that I have running software raid1. It looks like the installer got it right on all 3. IIRC, one was installed as CentOS 4.1, another as 4.2, and another as 4.3.
The installer will install grub. Just not properly. If the first disk dies, when the box comes up, the previous second disk grub stage 1 will load but it will not look for the stage 2 on the current disk and therefore fail.
Hard to believe the upstream provider of an Enterprise Class OS could allow raid bootloader configuration to not work on a very large percentage of machines for very long without there being hell to pay, and big headlines in the trade journals.
Heh.
Since I've switched to CentOS, I've been using software raid1 and everything seems to be working as advertised, including the support for /boot and / raid in the the installer.
Go get a spare box, install, pull the first disk and see what happens. Then repeat with FC5.