Well yes, water is good for weight loss to a point. If you find you're down on the scale during the weeks you drink more water than usual, that's because since your body is getting a constant supply of fluid, it's not having to retain any of it. The less water you drink, the more your body will hold onto. Give it plenty of water and *whoosh!*, it lets go of the excess, therefore dropping anywhere from 2-4 pounds of water weight.
It's great for flushing excess sodium from the body and it also helps your liver to metabolize foods and fats better. So yes, in many ways, water is good for weight loss. But not in the sense that some people believe when they say, "Just drink a ton of water! You'll lose weight!"
It's not quite that 'simple', I'm afraid, but it all works in the end to help metabolize fats better and keeping excess sodium (and therefore excess poundage) off of the body
Now, whether or not water helps speed the metabolism is, according to a recent study I read, still in debate. In some people, a higher rate of metabolism DID show after drinking ice water. Actually any cold drink will work because your body 'metabolizes' the cold drink to bring it down to body temperature, hence speeding your metabolism. But whether or not it's significant enough to even make a difference is still in question. I'm guessing not, but I'm no expert. I doubt it makes a significant difference.