I use a Camelback Fourteener and am very pleased. Sourced locally for $100. I remove the bladder for my commute. Carry a change of clothes and lunch. I leave shoes at the office. I like that it's vented on my back.

CamelBak Fourteener 24 Hydration Pack - 100 fl. oz. - Free Shipping at REI.com

I did 42 miles last Saturday and never gave a second thought to my pack