I've used bottled water, with no discernable difference. I've also boiled my water beforehand, and I think I would do more often if I could be bothered. I just use tap water with Campden tabs usually. I've only had 1 brew that I couldn't drink, and that was due to infection, I think.
I do read up a lot on water chemistry, I used to keep amazon tropical fish and had to completely change my hard, alkaline tap water to soft, acidic water; so I know it's within my capabilities. ( I still have my ro filter plumbed in under the sink, but it wastes a lot of water, so it is not used anymore). But I like my beer enough not to bother with all that hassle, and for me, that's what it's all about. ðŸËÅ