They are totally useless. Unless you have to perform a certain task. If you don't list every little thing you have to do to achive your goal, you may miss a teeny-tiny part, like updating fstab after moving directories. And end up screwing with the server all night long instead of 10 minute job.

BTW, if you use pygrub with Xen, extra won't work and you won't be able to boot domU in single mode, for example. You'll have to specify kernel and ramdisk and comment out bootloader instead.

http://en.miheev.info/2010/05/06/checklists.html