There are obvious pros and cons.
When hiking, I've never come across a situation where I want to have water as quick as possible in a quantity. For me using a hydration pack, on a never-ending ascend, is to make sure that I don't have to stop for long. I can take an optional pause every 200 steps, to sip some water, take a look around, take a picture and move. (I don't intend to say that one has to stop to suck water out of the hydration bladder).
I don't really need a spray of water at all.
So, on such a thing using something like a pressurized pack would be a too much trouble with an extra care it demands.
Same goes without saying for Rock-Climbing as well (where you can self-arrest and take a sip and then climb on, no Hurry!), Hiking, Geocaching, etc: To the activities for which the normal hydration pack serves the necessary purpose.
If I am cycling, be it anywhere, like be it off-roading, be it pure mountain-biking, be it BMX, Its more likely that I am going to pant for breath and I want to drink water as quick as I can in order to quench the thirst. Sucking the rubber knob does really annoy me, as compared to having a sip of water from a bottle, or even under a tap, but thats at the cost of a longer halts, which is is again annoying. So, I'd definitely consider having a pressurized hydration pack when I am cycling at higher speeds, mountain-biking, etc.