It depends on where you live. Some of my plants get tap, sometimes aired out first and some get filtered water. The filtered water makes them much happier. I was lazy early in the season and I filled up my reservoir w/ tap. The plants looked pretty bad until I switched to filtered and now they look great. It's not just the high chloramine in my tap water, it's also hard with a very high pH. I think my tap comes out at 300+ ppm. Even after a brita it's not great to drink. Other peoples tap water is just fine and other plant/soil combination such as turf grass can tolerate poor quality water.
Here's what I recommend for anyone:
1. Save rainwater if you can
2. Get a tap water quality report
3. Aerate or bubble tap water overnight
4. If plants are not healthy w/ #3 then test ppm and pH
5. If test is high then find a suitable filter
6. If filter is not an option try different potting mix or amendments to counteract chlorine/pH etc...
Haven't tried it yet, but an aquarium test kit may be an option. If you don't test your own water, talk to people at a local aquarium, hydroponic, or home brew shop. Someone at one of those places will know how pure your local water is.