You've already mentioned the cons.
The advantage of a hydration pack that doesn't require sucking on the tube becomes apparent after slogging up a long, hard hill.
Your diaphragm is already exhausted and putting all its energy into pumping your lungs.
Putting in the extra effort to create the vacuum necessary to suck water out of a straw suddenly becomes monumental.
It's a wonderful feeling.
outdoors.stackexchange.com/users/3933/saltface
Two things that haven't been mentioned in addition to the spray action is that Geigerrig has a filter that snaps into the drink tube allowing water to be filtered on-the-go under the pressure from the system.
This way you can refill from about anywhere---rivers, streams, etc.
Also, the reservoir can be turned inside out and washed in the top shelf of the dishwasher.
outdoors.stackexchange.com/users/5695/Robert
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.
outdoors.stackexchange.com/users/2303/WedaPashi
1) Can rinse items off.2)
A dog can use it.
:)
Someone gave one (Geigerrig "Rig 500") to me as a gift since he had leftovers from an event.
The reservoir had a traditional water reservoir (clear) and a separate air reservoir (blue), which was inflated with a small shoulder mounted pump.
Image below but picture the one used for taking your blood pressure.
Here's the unit on Amazon .
The use case my friend cited was that users could use the pressurized water to rinse themselves off.
Medical professionals have a sink on demand (cuts, eyes, etc) and athletes could wash off mud, rinse glasses, etc.
The use case I've found most valuable is actually running with my dog.
If we do a longer run I'll bring the pressurized reservoir in a smaller pack.
We can now go for longer runs without planning around water sources.
I'm not a huge fan of the pack
but like the concept
and it doesn't add too much
outdoors.stackexchange.com/users/4135/mattsolar
I have the Gerrig system and for me the primary advantage is the ability to spray water.
In really hot weather sometimes the most effective use of water is to spray it on you, rather than drink it.
This is easy to do with a standard cycling water bottle and next to impossible with most hydration packs.
Doing 8 hr MTB races, I have problems with muscle cramping late in the event.
Spraying water on my legs helps a lot.
With the Gerrig system I don't need to carry both a water bottle and a hydration pack.
It's also quite useful in muddy conditions to alleviate the gunk in the drive train.
While the pressurization is a nice benefit for actually drinking water, I don't think it's enough of a benefit on it's own to balance the trade off in extra weight and complexity.
Having said that the system I have works really well and outside of the extra weight has no other drawbacks in over 3 years of use.
outdoors.stackexchange.com/users/5348/Fred the Magic Wonder Dog
I saw an ad today for a pressurized hydration pack.  My first thought was "why?".  I can't imagine a scenario where this would not lead to (a) more weight, or (b) greater risk of failure... neither of which I'd care for.  What are the pros and cons of a pressurized hydration pack?
Why would I want a pressurized hydration pack?
outdoors.stackexchange.com
<gear><hiking><hydration-bladders>
outdoors.stackexchange.com/questions/6998
outdoors.stackexchange.com/users/127/Russell Steen
With the Gerrig system I don't need to carry both a water bottle and a hydration pack.  The primary advantage of the Gerrig system is the ability to spray water. The advantage of a hydration pack that doesn't require sucking on the tube becomes apparent after slogging up a long, hard hill. The system works really well and outside of the extra weight has no other drawbacks. The system is simple, it is good for long ascents despite the extra weight.
The system is simple and the only drawback is extra weight. Spraying water is an advantage, the system is great for long ascents.