I play the Grob.
I like it when players grab alot of central space. Its exactly what most flank openings are made to fight against. I suggest using a King's Indian formation against them. Solid and hard to fight, and add to that good attacking chances
I have a beginner's chess book, and in the openings section, it has a very small section on the Grob.
It starts with "With the horrible 1. g4, White grabs Kingside space..." and after throroughly slamming it simply says "When you're white, don't play this inferior opening". LOL. The author sounds like he has a personal vendetta against the Grob (maybe he lost to a Grobber in embarassing fashion?)
I played the grob for a while and it practically rips up your kingside so badly you shouldn't castle that way.
I remeber something like
When you're black, let out a cheer when you see 1.g4
When you're white, don't play 1.g4
Thanks to manik and estragon. I wanted to bump this up the page just to see if anyone who missed it the first time had any ideas.