Interesting to know. I've only played one game where someone used this opening against me though.
Grob openings suite
Keep in mind this thread is just for fun. For a more serious thread on the Grob Attack, I liked this one:
http://www.chess.com/forum/view/chess-openings/the-grob-attack2
I've never had anyone play the Grob against me, except for the computer program on this site. I lost. 
If one merely ignores the center for a while, a rich and intriguing new world of chess openings manifests itself, based on Grob's Attack (1. g4).
Center Grob
Grobidor Defense
Grob's Gambit Accepted
The Grobephant Gambit
Latvian Grob
Grobekhine Defense
The Grøbinavian Defense
Le Grobois
Pirc Grob
Grobilian Defense
Fool's Grob