Depends how you use them.Sniper weapons on the whole are rather unimpressive. I'm working on some homebrew rules that might make them a little more fun.
The long rifle and long las are perfectly adequate to take out juves and gangers.
Consider the plasma gun and melta.
They were designed, lorewise, to punch holes in space marines and tanks.
A specialist can do good work with a long rifle sniping lonely juves leaving your big guns to focus on the Brutes and champions.