IV would signifigantly decrease the halflife of the GH. It goes from 2 hours, down to 0.6 hours if taken IV instead of Subq.
which means a lot more injections are necessary. In theory, it is more effective, but you'd have to inject it more often, and IV injections 2-3 times a day are rough and leave track marks unless you have a painful catheter in you.
Also, it depends on waht kind of GH you're using. Getting a staph or a bacterial infection from an IV injection can kill you in less than a week. That sort of sucks if you ask me.
Also, wherever you shoot IV, it'll more than likely leave a painful welt, and you'll have to cycle through different veins.
IV, good in theory, but not in real life.
I'm debating IM or Subq now though, don't know which to try.