I would recommend everyone treat their potable water tank as if you would drink out of it. If it is so bad that you won't drink out of it, why would you wash dishes or take a shower with it? Think about it!!! Potable water is safe for drinking, washing and bathing with. If you don't keep your fresh water drinking tank up to potable water standards you can have issues even if you don't drink it.
The reason I fill up at home is because I mainly boondock. Where am I going to fill up when I'm on the road? I take a quality filter and a good regulator with me just in case, but I know the quality of water that I have at home. When I fill up at an RV park, the filter and regulator is always used. For me, carrying 666# for 80 gallons of water vs. 166# for 20 gallons of water makes no difference in my towing or fuel mileage.
As far as trailer quality goes, there are some of the most expensive units out there that have had issues with folks towing the trailer with full fresh water, gray water and black water tanks. This issue isn't necessarily a cost issue.
The recommendation of folks checking their water tank mounts is a great idea.