I agree, the Camelback sounds hot compared to water bottles. Just did the MS 150 in SC, and I don't think there was ever more than 10 miles between stops. The SAG is incredible, both the food/supplies and the people working the stops.

I second the camera idea. Suggestion: disposable, under-water camera, so you can stick it in your pocket and not worry about the sweat getting inside it (which happened to me on a different ride). They are usually small and light, too.

Pack as lightly as possible, and in a wheeled bag, because you may have to lug your stuff further than you'd like.

We had to bring our own energy bars because we had no bar sponsor. (We did, however, have a beer sponsor--at the overnight site, not on the route!--which I would take any day over an energy-bar sponsor. )

Have a great time!