100% agree that the quick release valve is worth every penny.
I will say that a downside to USWE bladders is that the bite valve starts to drip after a year or two of use. I’ve had it happen to multiple valves, and it’s not just that I do something weird with it because my wife had the same issue.
Our “team” USMES, is sponsored by Osprey which uses the same bite valves. I personally despise them and replace them with Camelbak valves & shutoffs. Still need to replace valves once a year though.
I max out at 3l in my Osprey Syncro 12. It’s a LOT of water, but the Syncro 12 is also my pack mule. EVERYTHING goes in there. I have done the Unbound 100 with it (one bladder refill) and use it when I’m going longer than say 50 miles. Just not enough pockets to carry all the stuff I want to.