I think it's really a personal choice. I don't think anyone can say to someone else that tap water is good enough. Some areas may have great tap water while others have theirs pumped full of flouride or other harmful chemicals.
I used to think Tap water was fine growing up, but i grew up in Canada where our water was relatively pristine. I can even remember a camping trip we took when I was a kid in Girl Guides. I can't remember where we went, but I do remember visiting the same place on a school day trip in the 8th grade, and The water was so clear & pristine, you could drink it right out of the stream. Yep, we dipped our cups into the stream, and drank the water straight, and it was cold, clear, refreshing, ...the best tasting water you ever had in your life.
Then in 1986 I moved to Southern California, and got the shock of my life. There was noooo way I was consuming tap water in Southern Cali. I didn't even like to shower in it. You could just feel all the crap in it, and it left your skin feeling dry, scaly & itchy.
In the early 90's, I was introduced to a network mktg company that sold activated charcoal water filters, that primarily took the chlorine out of the water. I started watering my plants with the water that came out of the unit, and couldn't believe what an incredible difference it made. I saw my plants flourish.
I stopped drinking tap water after that, and switched to bottled, even though the tap water was still palatable. I preferred Appollinaris.
These days, the tap water quality in Ontario has gone so far downhill ever since consecutive budget cuts by both the Harris & Eves governments that I won't drink tap water anymore. I know some people who ever since the Walkerton disaster, insist on boiling all the water before they drink it. That doesn't do much to filter out chemicals, but it might help with e coli or other biological organisms that may be present. For the most part, I think bottled water companies have stumbled onto an unregulated niche they've turned into a cash cow, but there are some bottled water companies that produce great stuff.
The best bottled water I've ever had was one called "Spirit of the Earth" Water. It comes from only 1 source. A spring in northern ontario, and it's hand bottled, so they can't really produce alot of it. The water is naturally filtered and comes up through layers & layers of a crystallized magnetized igneous rock in the Canadian Shield thousands of years old. It supposedly took 2,000 yrs for each water molecule to reach the surface or some such claim to fame... but the idea being the water is actually alive, naturally magnetized, and in harmony with the natural rhythms of the planet, and therefore with humans. I don't know if all the hoopla surrounding it is accurate, but I do know this water is amazing. The idea being that the natural magnetism in the water causes it to go through your body like little scouring brushes and pick up all the waste and flush it out of your body. I believe it. I would drink a few 2 litre bottles and would feel such an incredible difference, and my skin would clear up, radiate & glow.
I think they did experiments in the UK flushing the water pipes with magnetized water, and it removed all the crud in the pipes. The tap water that's pumped into our homes is essentially recycled water that has had all the life taken out of it. It doesn't pick up crud along the way... either in our pipes or our bodies.
I'm under the impression that the best filters to get are Kirby reverse-osmosis, due to their ability to remove more than simply chlorine, but also chemicals as well, but that it can also result in a huge sodium intake.