Let me not go into how much more cooler zsh is. The problem is that, it simply has too much going for it that there is no good starter .zshrc file. This means that a stock install of zsh is going to suck and one wonders what were all those guys smoking when they had simultaneous moments of ecstasy while using zsh.
Yet, Being able to type gcc -[TAB] to see a list of its command line options is something that most users could never imagine in other shells.
I have my own zshrc here - this is the same config file that I have contributed to Slitaz (which by the way is an entire linux distro with wireless and everything in 25 mb). The zshrc is annotated to save others the pain of finding out things to google for. It more or less gives the same user experience as bash - with ESC-Backspace, Ctrl-a, Ctrl-e, etc.
The OS would be a much better and more maintainable place if everyone moved to zsh and its scripting.