yep.. that's exactly how it works.. I've done several raid1 software mirror installs.. Normaly I do this with an initrd, and not with putting md directly in the kernel. The initrd is loaded by grub and that loads the correct kernel modules required for booting the arrays

A couple of other pitfalls that people should pay attention to:
If you use LVM with software raid.. make sure you edit the lvm.conf to force it to ignore the direct access partitions.. bad things can happen if LVM writes to one of the devices and not the raid device.

damn.. that's all I can think of right now..