I have a squad of ten Scouts that I use pretty regularly that's armed with nine sniper rifles and a heavy bolter. The heavy bolter probably defeats the purpose of stealth as well, since the discharge from a bolt weapon is supposed to be a fair bit louder than firing a rocket.
They're useful for general anti-infantry ops, though. Infiltrating really isn't about getting closer to the enemy per se, but it's about positioning your squads with the capability in reaction to how the opponent has deployed. I've found that sticking the squad in heavy cover of some sort and letting them sit tight for the game, taking potshots at targets of opportunity, tends to work pretty well. They also tend to win their points back in a hurry against Tyranids-- snipers do wonders against the big 'uns. I tend to bring the heavy bolter just sort of as a stopgap measure if I have to halt an infantry mob quickly--snipers are just as effective against Orks, Guardsmen, Eldar, and the like as a boltgun, but the heavy bolter scythes right through 'em, and having that extra kick when you need it is good. Forfeiting the sniper shot against monstrous creatures for three shots that won't wound it most likely is a fair tradeoff when you've got nine other guys in the squad.