I'm a believer.
I've converted from Nalgene to HydroFlask for my everyday work water bottle. The flask's ability to keep water cold is a major plus (something I didn't even think I'd care much about until I started using HydroFlask and the advantage was clear), and the versatility really wins it for me (I can use it for coffee or drink mixes without having to worry about it retaining scents the way Nalgenes do). Also, this thing is a beast. It's almost (just almost) too large to carry around frequently but come on, it's worth it. It holds a lot of water.