The biggest complaint I hear is a sweaty back, but in hot weather a Camelbak full of ice feels great. I don't usually use one, but have tried it in the hottest weather in the desert SW and it was pretty nice. Filled with all the ice it would hold in the morning it was cold all day. Personally I prefer drinking from bottles in general though. Just personal preference and likely more habit than anything else. Also I find it easier to fill bottles at convenience store drink dispensers. Much of my touring is where I refill multiple times per day.

In hot places where you need to carry water for all day a big Camelbak is tough to beat.

I do often still carry a little backpack with a light load even when using bottles. It is a good way to keep a few items handy and to have valuables automatically go with you. A Camelbak would do the same.

If you like your Camelbak it can be a great way to go, especially where you need to carry a lot of water.