Each clue on the grid represents a regular expression. The row of cells it points to must match this expression exactly, where it is read starting from where the clue is drawn. There is a unique way to fill in the whole grid.
http://kottke.org/14/01/regular-expression-crossword-puzzle (http://kottke.org/14/01/regular-expression-crossword-puzzle)
One of the rings of hexagons in the grid contains a lot of X's. Indeed, it alternates between X and a different letter if you travel around it. The other letters spell ARMORED RECON when read in the correct order and direction.
No, I haven't solved it...