I used bash first, then zsh. You have to try fish, it shows a "ghost" of the first matching autocompletion on the same line, which changes dynamically as you type. It also has a cool memory effect for figuring out history completions based off the directory you are in.

Like csh on FreeBSD, alt+(up/down) can be used to search history for arguments instead of lines, so if you do something like

   touch some/long/directory/path/to/file
   ....
   rm so<ALT+up>

fish will search all individual arguments (correctly handling quoted spaces, etc) for arguments starting with "so" and it'll suggest the path in question, even though the head here (`rm`) differs from the original (`touch` in this case).