i would say that powerful is an understatment anyway here is a mini review/setup guide
what i like is the comprehensive auto complete that is program sensitive and will even complete flags passed to the program (such as --do-somthing, i would type --do-<tab> and have it auto complete )
the regex everywhere is nice and is mostly bash compatible and there is a whole lot of stuff you wont use like bieng able to redirect a file to a tcp socket (for those who want a zsh webserver)
there are one or two things i couldnt live without such as the history bieng shared between all open zsh sessions, a real life saver and auto complete on history as well
if you are going to use it i recomend looking into grml.org and the zsh lovers guide as it is very comprehensive and the grml live cd is my personal fav debian rescue CD, it ususes screen and zsh by defalt and is patched for things like low latency and rieser 4
