ag is often faster when you're using it interactively, replacing "grep -r" (in particular in version controlled dirs). It's also faster in the sense that for interactive use it will often DWYM.

But has too many weird quirks that it can replace grep for data munging. E.g.

    $ ag verb fullform_nn.txt >/tmp/verbs
    ERR: Too many matches in fullform_nn.txt. Skipping the rest of this file.

Man ag says there's a --max-count option. Let's try that.

    $ grep -c verb fullform_nn.txt
    206077
    $ ag --max-count 206077 verb fullform_nn.txt >/tmp/verbs
    ERR: Too many matches in fullform_nn.txt. Skipping the rest of this file.

Wtf? (and running those two commands with "time" gave ag user 0m0.770s while grep had user 0m0.057s)