Also known as a "boot manager" ;-) I've been using Superboot and XBoot since 1990 or so, it's one of the most useful tools I have. A open source boot manager would be great, but it should be able to do more than selecting kernels. To be useful, it must have all the functionality of current boot managers, otherwise it would be just another thing to slow down booting.
I think this isn't / shouldn't :) be Peter's goal -- kernel loader is something totally different from things like XBoot etc... It's true our world differs a little from Linux one (and therefore comparison with LILO, Grub etc isn't 100% correct) but I'd prefer to be more kernel loader (as the last binary in AUTO) than boot manager (as the first binary in AUTO).