I experimented for a bit with cycling with a camelbak. After 3 decently long rides with the camelbak, I'm going back to waterbottles. (Yes, they're heavier, no, I'm not getting rid of my Camelbak completely --- it's still a great solution for hiking)
- Balance. When cycling, the camelbak has a tendency to slip and then put all the weight on one shoulder or the other. This is extremely annoying, and at times painful. And all the contortions I go through to try to correct that while riding is dangerous.
- Comfort. Having something heavy on my back when it's hot is uncomfortable. Plus it puts pressure on my lower back, which already is the most vulnerable part of my muscle groups.
- Hygiene. I like having one bottle for Cytomax or other sports drinks, while having a second bottle for just plain water. If I put Cytomax in my camelbak, I'm stuck with Cytomax and no water, or I have to put a water bottle cage on my bike, in which case why not reduce back pain and have no camelbak? If I carry just water on my Camelbak, then I end up using Endurolytes or some other pill based stuff, which just isn't as effective as Cytomax (because I have to stop to take them). If the point of the Camelbak is aerodynamics of saving weight, then having to stop to take Endurolytes kinda defeats the point, doesn't it? On top of that, once you've put something like Cytomax in your Camelbak, it's impossible to clean it out completely, so you risk your Camelbak gunking up and becoming a nest of horrid biology experiments.
By the way, the Camelbak is unbeatable for hiking. It lets you drink while walking, and it carries a lot more water than a few waterbottles. I frequently find that I drink a lot more than I normally do, just because it's so convenient.