I have used bash for over ten years. I just got a little curious and decided to study the competitor zsh.
I think it has a killer feature: shared history. The previous commands will be shared between instance of zsh. I find this very handy since I always run several shell with scree. The following lines turn it on:
# History sharing and huge size HISTSIZE=10000 SAVEHIST=10000 HISTFILE=~/.history setopt share_history setopt append_history
I am not sure I will switch to zsh but it's interesting to change things a bit.