i live in LA, but when i'm in new york city, i drink tap water when indoors (it's always nice and cold and delicious even when it's hot out, i don't know if this varies building to building) but when i'm out, i always buy cheap bottled water (poland spring or crystal geyser) because i don't want to carry a non-disposable water bottle with me when i'm out and about. new yorkers are out most of the time so that would explain it.
LA tapwater is nowhere near as good, in fact it's downright disgusting in some parts of town, but i drink it anyway when i'm at home because buying large amounts of bottled water is a pain in the ass (heavy, bulky) and expensive. sometimes i'll buy some perrier or pellegrino if i want a treat. i've found that if i fill several large mason jars full of water and put them in the fridge, it's a good compromise. a lot of the shittiness just evaporates out. i'll grab one and put it by my bedstand before i go to sleep, for example.
at the office we have the standard 5-gallon jug water delivery service which is the best. i might start getting the service at home, honestly.