What he said.
The other disadvantage to a camelback is that you have no idea how much H2O you have remaining. If you fill up 3 Nalgenes you know precisely how much is remaining after each stop to drink.
If you aren't accustomed to altitude, understand that you SHOULD be drinking more water than what you normally intake (a lot more). The challenge is when it's not hot and you reason; "I'm not thirsty and water is heavy, why should I carry that much?".
I carry and consume a lot of water, and I avoid altitude issues. I typically take two standard size Nalgenes and one of the jumbo 48 oz. I drink as much water as I can stomach each morning before leaving camp (I pee a lot on the hike in) and then I'm pretty thirsty at dinner.