I've heard the pH has been changed and can affect your stomach but personally I prefer the taste as I find it difficult to drink lots of plain water.... I thinkk in the scheme of things it's probably better than eg diet Coke which is very corrosive and full of additives.....
Fizzy water has been proved to be better for you than still. It is also better for your teeth than still as spoken about in Scotland on sunday paper an article in there states that it is