This seems like a good place to once again plug fish[1]. Exactly those goodies I want in a shell and the autocomplete is so convenient I no longer know how I lived without it.
I've just installed fish and it doesn't support bang (!) history nor some basic scripting tools (eg $?) which makes it pretty useless for power users.
I can see how the colours and suggestions are great to those who are new to the command line though and there were some cool features (eg highlight search phrases from grep). But most of that stuff is just emphasising stuff you'd learn to spot anyway, after using the CLI for years.
So as cool as it is, I really would find it more of a hindrance than a help.
I'd just like to second this. Though bear in mind that many things assume you're running bash on OS X, e.g. the homebrew installation one-liner doesn't work with fish.
Also, note that you can easily copy across your bash settings using:
And there's all the other cruft removal.
[1] http://ridiculousfish.com/shell/