I bought a Sigg reusable water bottle a year ago - and haven't looked back since. With all of the recent research indicating that plastic leeches into our drinking water and causes cancer, plus all of the environmental damage done by both plastic production and disposal - having a metal reusable water container just makes sense.
I have noticed that since I always have it with me, I also drink a lot more water than I did before.
My only recommendation: get one with a finger loop in the top instead of a plastic dispenser. They get heavy to lug around, and are awkward and slippery - so the loop helps it stay in hand. Plus I noticed that the dispenser didn't give me enough liquid at one time. You can never take in too much water - so I prefer to be able to guzzle at will.
This bottle holds one liter of water - and costs less than $10. Foxy!