I have one of the women specific camelbak's (the dream I think) and prefer it. I think I made up my mind to go w.s. when I saw a woman wearing a non-women specific one, and the strap that's supposed to fit across the top of your chest hit her just below the bust, forcing boobage up and over the strap. It looked VERY uncomfortable. The w.s. one's are designed to avoid that. Whatever you get, simply try one on first! I have to say I stopped using the camelbak halfway through last summer though. I found that on 95% of my rides I had places to stop for free water refills, so I went with the polar bottles. You will end up with a sweaty back at 90 or 100+ deg. and with the camelbak on I simply noticed it more; they're designed to wick away moisture but you don't get the cooling sensation made by the wind as you whip along .

For heat... I agree with all of the above. I pack bottles with as many ice cubes as possible, then fill the rest of the way with gatorade. A friend told me that it takes longer that you think to fully hydrate, and that if you're doing a long ride (like a century), start consuming xtra water a day or even two before. You do have to just get used to the temps... we've got a good amount of humidity and hi temps in san antonio, and there have been days where our team rides have been canceled simply because it's so hot (not that some of us didn't go out for an easy loop anyway, lol). It's funny during "winter" most of the time it didn't get below 35 yet I always wished for summer. Now that summer is here, I wish it were cooler again! lol.