i think it gets a lot of hate because a lot of noobs just launch it randomly. they just shoot off two quick shots then go camp. i can't think of any times i never saw the person when i used it. i just use it when i am too far for a gun or they are camping at a funny angle or under cover.
Yeah, I always use it when I actually see someone. I don't think it's really that "noobish" of a weapon though. At a distance it's a one shot kill with a pretty wide hit range, I will admit that. But if you stumble upon somebody in close quarters then you either have to be dead on accurate or you're most likely dead.
I actually really like the perk setup for the default "grenadier" class. Stopping power makes your bullets more effective, scavenger lets you pick up more grenades for the grenade launcher, and commando makes you better in close quarters. I've been using that class a lot lately...