This is excellent advice. The "cleanliness" of the fuel is a direct result of the type/frequency of the maintenance performed by the station operator and his supplier. Tanks should be periodically checked for water and pumps should have their internal filters replaced routinely. A crappy looking station or pump is probably a good indication of poor maintenance.
I worked for a Shell supplier for over 15 years. This company also owned a terminal on the Texas Eastern pipeline. All the fuel is exactly the same until it is loaded into the tanker to be delivered to the station. Our Shell additive was metered in at this time...unbranded stations of course did not get this additive, although all the fuel coming up the pipeline had some amount of detergent in it. The "premium" brands add more while loading, so there really is a difference.
It's hard to say if it's worth a .20/gallon premium, however. I generally run Shell (old habits die hard), but will occasionally run cheaper stuff to save a few bucks. Hope this helps.