I got started using these when I lived in Las Vegas. When you ride past the last houses there you have no chance to refill a water bottle. The 100 oz capacity and the ability to carry a snack is great. Comfortable enough to use all day.
You get what you pay for with Camelback. A great product, but pricey. You are paying for the name. That being said, it simply works. I've done 2 hour trail rides in 100F heat with the reservoir 1/3 full of ice and the rest water. I've finished the ride with some ice still in it. It keeps your water cold. As for riding in the heat, with such a large pack on your back, I was surprised at how non-intrusive it is. I'm large (6'5 & 220lbs) and the straps first me well, nothing rides up or down, the mouthpiece is located conveniently. Some other reviews complained about being able to get the reservoir into and out of the pack when full. I have not had this issue. It's been easy to get in and out even with a full reservoir. I'd buy it again, but wait for a sale.
Use it to carry clothes and lunch for daily commutes without the bladder. Use the bladder on long rides when a water bottle may not be enough. Plenty of room to stuff layers, food and whatever else may be needed.
ive had mine for over a year and its really aerodynamic for my rides. holds a lot of water.i use it as a back pack too. the best backpack i ever had because it serves as a backpack and a hydration pack has an ipod pouch