I recently pulled the trigger on a USWE Airborne 3 after using a Camelbak and many other hydration packs for many years, after a few rides here's my take.
Local prices are insane @ SW they were 3.3K I got mine overseas online from BikeInn for 1.2K
It has a top fill bladder so a little more difficult to fill - I remove the bladder, which is no big deal as it means you can at least inspect the bladder for any funny stuff growing inside at the same time - the Camelbak you can simply open the cap and fill.
When i first tried it on, I thought Wow! this harness is really small and tight ! I did get the largest one they make in this model. It has a 2L bladder that i fill to max 1.5L. I found the velcro adjustments on the harness really worked well, you set the harness while its on your back and the velcro is serious HD stuff. Once its setup, it sits high between your shoulder blades and their "No dancing Monkey" hype certainly works well - Its sits properly on your back and doesn't move around at all even in the rough stuff.
Mine has a detachable tool bag which I remove for normal rides as I have a tool clamshell mounted on my seatpost - I would probably use the detachable tool bag on 100 mile events - So besides the water there is a waterproof pocket that i can fit my phone, car keys and spare AXS battery - for night rides my helmet light battery fits as well - The magnetic goody for holding the mouth tube really works well.
The water doesn't heat up any worse than the Camelbak which has never been a issue for me.
Sweating on the back and shoulders is also no worse than Camelbak, in fact the USWE has better ventilation on the back padding and harness than any other hydration system i've used.
On my first ride I didn't think i would like it as it sits very high and feels fairly tight on the chest, but 30 min later i was wow this thing works really well, the harness is elasticated so it doesn't impede breathing - And I blow like a train on the hills - It basically feels part of your body once you ridden a couple of hours with it.
As i mentioned earlier - Locally they insane with their prices - 2K difference I cannot understand how they even stay in business, fortunately i'm in a position to order online when i'm in Europe or I would still be riding with my Camelbak .