There seems to be a lot of theories about drinking water; however, I'm agreeing with Kelly, and going by the guidelines that WW has set for us. After all, they hire the professionals who do the tests and they do update their findings when they see fit.
The question is how much water do I drink? At least 6-8 glasses of water daily which always include my milk servings. I am finding that some days I may drink 8 glasses of water PLUS my two milk servings which make a total of 10.
I also find that the weeks I cut out diet caffeine-free soda are the weeks I lose better.
Good luck! And yes, I do believe there is "magic" in the water!