I'm playing around with fish since a couple of minutes and one zsh completion thing I am missing is "fuzzy" completion. In zsh with the following files in a directory:

    log-20120103
    log-20120104
    log-20120503
    log-20120603
    log-20120604

I can do: "$ less 603<tab>"

And it will complete to: "$ less log-20120603"

I cannot recall whether I had to specifically enable this in zsh.

The variant that I most miss is the partial completion on paths. With zsh I got into a habit of `cd c/s/b/<tab>` and having it expand to `cd code/sites/blog` so long as the tabbed path is unambiguous.