If you are using RAID 1 kernel mirroring, you can do that with /boot too, and Grub finds the kernel just fine. I've done it many times:
Hmm, OK. I wonder why anaconda doesn't do it then.
Reading various websites, it looks like grub2 can do it, but you have to make sure that various grub modules are installed first - i.e. do something like
grub-install --modules='biosdisk ext2 msdos raid mdraid' /dev/xxx
I don't know if they are added by default these days.
The other gotcha is, of course, that the boot sectors aren't RAID'd - so if /dev/sda goes, replacing it will make the system unbootable since it doesn't contain the boot sectors. Hot swap will keep the system running but you have to remember to re-install the correct boot sector before reboot. If you have to bring the machine down to change the disk, then things could get interesting!
P.