Every once in a while I'll still hear that you aren't supposed to count caffeinated drinks in your daily total because caffeine is a diuretic. IMHO, that's not right because the amount of water you lose from the caffeine is much less than the amount of liquid accompanying it. So, it should all count.
Something else I've heard lately is that 64oz. is actually overkill too. There was a doctor on some show I was watching a few weeks ago...I can't remember what it was, darn it...but he said that you get so much liquid from just food that you get a lot of your daily requirements from what you eat. If you think about it, it makes sense. Soup, fruit, tomato sauce, pudding, all of that is mostly liquid. I don't know how to count that though, so I'll just stick with the 64oz until someone gives me a different number!