I said it. I don't like to as I don't like to have my water sitting in a hot water tank as they reputedly leach out copper and other metals from the tank and pipes. My cold water is mostly through plastic pipes. Running the hot water for a few minutes is no cure as it still comes from the same (metal) tank.
I use cold tap water , and to warm it boil up some in a kettle and use that , 1 kettle per bucket. I have no problems doing this, but have had problems when I've used hot water from the tank.
I can physically taste the difference between my cold water and cooled water from the hot tap, and if I fill 2 tanks I can see a difference - the stuff from the hot tank is cloudier and gassier. This has been true for every house I've lived in, with both modern and ancient plumbing. The only situation it might not work in is if you didn't have a hot water storage tank, but heated with a demand heater (probably gas only?), but you only see this on one bed or studio flats I believe as your flow rates are pretty poor.