Maybe it's time for a payload FAQ? I know we have over 5 payloads in common use and maybe a faq or a table on linuxbios.org could show the features of each? Off the top of my head, we have:
Linux Kernel regular - use as your OS kernel
Linux Kernel Kexec bootloader - boots another linux kernel from a device supported by linux (I don't know where this payload stands as a formal package)
Memtest86 - great memory tester
Plan9 - Plan9 OS (can it boot Linux yet?)
ADLO + Bochs BIOS - Interrupt support, boots BSDs and Win2k
Etherboot standard - kernel over ethernet
Etherboot devel branch - kernel over ethernet and raw disk i/o
Etherboot 5.0.6 polled ide patch - kernel over ethernet and buggy file system support
Etherboot SIS patch - kernel over ethernet, file system support, and booting WinCE I think (but I don't know if SIS has let this out formally)
RedBoot - could read the file system but never had the elf support to make it really usefull
Steven James ELF finder - I think this was written as payload? Anyway, it lets you choose from payloads in your rom.
And I'm sure there are probably many more which have good uses too. Please, add on to the thread if you know of more.