Water quality is important in influencing the outcome of a brewed cup of tea. As I explained a long time ago, I recommend avoiding using bottled water for brewing tea. There are compelling reasons to use tap water instead, both from the standpoint of health and safety, and in terms of promoting sustainability and efficient resource use.
Even though I always use tap water to brew tea (sometimes filtered tap water, but always water that originates at the tap and never bottled water), I have definitely preferred the water in some places to others. My favorite water that I've ever tried was the tap water in Cleveland, Ohio, which is taken from Lake Erie, pictured below:
Beer, like tea, is also greatly influenced by water quality. This is one reason why the beers brewed by brewing companies like Iron Hill Brewery, which brew beers on-site at each of their brewpubs, taste different in different locations. I find it no coincidence that my favorite beers in the world, those produced by Great Lakes Brewing Company, are also produced with Lake Erie water. Lake Erie water gets a bad rap, because of the long history of pollution in and around Cleveland, and it may not be the cleanest or safest tap water to drink, but when it comes down to it, I think it tastes great.
When I lived in Cleveland, I did drink tea, but I was not as into it as I am now. I have not had much of an opportunity to brew tea using Cleveland's tap water, so I can't say how it performs for brewing tea. But I know that when I have visited, even just filling up a cup of tap water at someone's sink, it tastes so good; it's one of the many things I miss about living in Cleveland.
This is just one of my random personal opinions, however...if you want something just a tad more objective, I'd recommend reading Cities with best and worst tap water on Yahoo! Green. Cleveland ranked 72nd out of 100 on their list. However, this list was based on safety, not taste! I suspect that if the cities were ranked by taste, Cleveland would rank much higher on that list.
Update: Yahoo! took their article down for some unknown reason. Thanks to Gingko for pointing it out.