They are fantastic but I have had trouble with the big one holding together, HOH was awesome with replacing bits that stopped working. When they work they are the best, but if you need one buy 2 as to have a spare around. I think of it as the Ferarri of humidifiers. Also, the Humidistats that he sells as controllers are the new standard in my room, I bought 4 to have a couple for future considerations.
About what water to use, what ever is in the water you use will b e floating around and collecting on all the surfaces in the room. So know what is in your water and act accordingly