Slater, boiling won't take out the excess organic materials or minerals. RO or distilled water is much better.
You might check around, a lot of supermarkets have RO machines in them-you bring the containers that are cheaper per gallon than the prebottled distilled stuff.
I use straight untreated tap water and have in Fw and salt tanks since the late 70's. I also have tanks filtered with various plant life. And use cold water from a frequently used faucet and let the water run for a minute before collecting it for the tank.
I trust the plant life to provide a better environment for my tank much more than any man made filtering or chemicals.
I tend to use tap as well, but have a fairly effective water softener that, according to my tests, yanks most of the hard stuff out of the water.
A few weeks ago the softener ran out of salt, and I didn't realize it till after I had done a water change. I was wondering what the 'f' happened after I saw hair algae grow rapidly after the water change when it never does before. It's nice to have plants to out compete the nuisance algae's, but it's not practical for everybody.
In emergencies (ie: when I'm to lazy to go get water ) I use tap water with a double dose of prime. Never had a prob, but again I dont always do that. The water in my area tends to be very good though....