Statistics are important, but you also have to consider the players involved. At this point, the consensus is that 1 g4 is unsound (the kingside thrust comes way too early), and my guess is that if 2700+ players started using it against each other, Black would be winning a much higher percentage.
Then again, IM Michael Basman has had some nice games with it.
I've noticed a lot of posts about this opening mostly people claiming that it is not a good opening for white. I have never played this opening, and I have never played against it. I have also not studied this move at all, so I do not claim to know if it is good, bad, or questionable. Admittadly if I where black and I saw this move I would consider it questionable, but again I have not studied it so saying that is just my "first impression" of the move. Just out of curosity I looked it up on www.chessgames.com and found that there database only has 234 games where white played 1.g4, however white won 59.8%,lost 29.5%, and drew the other 10.7%. The database at chessbase.com turned up 2000 games after 1.g4 (it only displays 2000 games at a time) and by my count white won 38.4%, lost 39.45 and drew 22.15% so maybe it's best to say that 1.g4 is unclear? I will look for other databases and post the results in the future. Here is a nice short game played by Henry Grob
.