@ rooperi: I myself have lost immediately against the Larsen (b3). It was one of my first tournament games and I simply panicked. But I was both inexperienced AND I have some anxiety problems.
I have a friend who also won with the Grob, mind you.
But those openings are only as good as somebody has never seen them. A decent player just needs to spend an afternoon to prepare against each of them. So you are seriously risking to give away your white advantage for nothing.
I played this opening for a couple of years all the way up to the weak USCF C class. One day I was going over the book that IM Yuri Lapshun wrote on this opening when I found myself thinking that he had some nice tactical wins. How did he develop that ability? Did he work his way out of class level play with 1.b4? No, I figured he learned to play chess first,probably with more mainline stuff, then started playing 1.b4. It was then I decided to give 1.e4 a try, not even knowing much theory. Having played both I can tell you 1.e4 gave me easier games and quicker wins. My rating also improved more quickly after that and I felt it developed my tactical ability as I became more comfortable with open games. I've never gone back to 1.b4 since then.
cheers rooperi i have just started to play it and am finding it very good both as white and black,i think it is the best opening i have played . i have had some good win's over higher ranked opponents with it ,though i have also been well beaten sometimes as well but i think that was mostly down to mistakes by me and not the opening.thanks for the comment