You can't snipe anyway as the kill cam gives away your position (unless you keep the scope held down for a few seconds after the kill - even then experienced players can work out where you are). Silencers mean when you fire your gun you don't come up on the radar - sadly they completely nerf the sniper rifle, so it's pointless to equip them on that gun (takes two shots to kill, which defeats the object!)
Air support (UAVs, Predator Missile, Pavelow, Chopper Gunner, Harrier, AC130) is a nightmare until you get cold blooded - having said that I use an M4 with stopping power equipped most times. I've just learnt to run into buildings when someone gets a kill streak reward going.