I use #! because Archlinux has taken some unfortunate turns and the sttitude of the developers has just been too sour to ignore. Gentoo was and is a nice distro but I just don't have that kind of time anymore just to keep things running.
#! gives me almost 100% of what I do to customize an install without any effort. CoreNominal has a real winner here! Thanks for all your hard work Phillip!