It seems an order of magnitude slower to me:

    $ time grep -r some_token .
    real	0m0.467s
    user	0m0.252s
    sys 	0m0.215s

    $ time ag some_token
    real	0m2.948s
    user	0m0.112s
    sys 	0m3.083s

(Both run twice to ensure the disk cache was warm).

Am I doing something wrong?