Around our house, we use tap water almost exclusively, but interestingly - there are lots of people who simply don't believe this is safe. Our own situation is a little tricky, in that we have our own well, and we do our own R.O. filtration for the main tap where we usually drink from. But this "lots of people" quote comes from a recent article on Skepticality regarding this very topic.
I encourage you to click this link, or the link above, for a read (listen) of this fine work from Derek and Swoopy.