You'll hesitate until the first time you use it, and see the crap left on the filter.

I got banned from one filling station for using one, always suspected their fuel, so one day when I knew the pumps would be quiet I took the filter (short piece of pipe on the bottom to angle into the tank) and put 40 litres of (shell) diesel in the tank, took about 3 times as long as normal, the manager comes out and asks me WTF I am doing, I was at 40 litres and WAS going to finish filling the tank, so I stop, the funnel drains down in about 10 seconds, and there is a cup full of water in the bottom, I show this to the manager and tell him it is water, he says no it ain't, I ask him to get the pink dipstick paste that all fuel stations carry, he claims he doesn't know what I'm talking about, I offer to try to set fire to it, by this time three other customers have come over and looked in the funnel, and all have driven away without buying fuel.

So basically I pay up and am banned, fine, I was just proving a point to myself anyway and already intended not to go back, they were normally supplied from the depot I mentioned earlier with the water table problems.