>It might still turn out to be, if you see if you can get a faster C version of wc.

You definitely can, at least if you allow manually vectorized code.

On my system, with a 1.661GB file (256 times big.txt from the original Haskell post) GNU wc takes about 6.5s (real time), a stripped down version of Apple's implementation about 4.1s, and a single-threaded vectorized wc (written in C) only 0.27s. (These times are of course only with a hot cache. For reference, catting the same file to /dev/null takes about 0.18s.)

edit: corrected the time for the BSD-derived implementation