There are no valid studies that show benefit for adults (including Barry Bonds) - there are benefits for children with thyroid problems as it stimilutes their growth deficiencies. If there were provable benefits we would all be taking HGH - the market would rise faster then viagra or cocaine.
Now there's a simile that says more than I wanna know.
Actually there are provable benefits. There have been many studies based on injecting HGH into seniors with pretty amazing results.
It is, however, very expensive.