I consider the PCV valve essential. It keeps the oil cleaner inside the engine, helping it last longer. It also keeps that stinky smell from getting into the engine compartment making a oily mess, and the smell always makes it into the passenger compartment.
You will sometimes get a gas smell also, since your gas tank is vented to the charcoal canister. Don't cap the line off running down the frame to the gas tank, or you may find yourself sitting along side the road with a non-running truck. Or a truck that seems flooded on a hot day. That line lets the fuel tank breath. They didn't want those gas fumes in the atmosphere, so they put them in the charcoal canister, and then they had a system to purge the canister and let the engine burn it. Each one of those vacuum lines has a job to do. It's good to know what you are taking off, even though you are not going to put it back on.