Galactus is no longer the Lifebringer but the World Devourer again. The Silver Surfer decides that keeping Ultron from taking over the universe and enlists Lifebringer Galactus to devour the planet that Ultron is on to stop him. That this tradeoff is worth it is extremely debatable. I don't like that any future genocides committed by Galactus are now directly the Surfer's moral responsibility.
In Ultimates, Galactus went through an ordeal at the hands - or rather faces - of Logos, who wanted him back as the devourer, and came out the other side determined to be the lifebringer. Just because the Surfer says "awww...go on" to beat the threat of the month he throws that away?