Finally pulled the trigger after eyeing this for a couple years because I wanted something in between my 1.5-liter and my 3-liter packs, and this fit the bill.
I bought this for long distance gravel cycling events. I received it one day before the Open Range 200k in Pratt, KS, and ignored all the conventional wisdom about not trying out new things on the day of a race. It performed flawlessly.
First off all the hype about not really noticing it is even there is pretty much spot on. I barely noticed it was there, and it was secure and didn't shift around or bounce like my other packs.
The way the bladder inserts (basically you just drop it into the pack) is a vast improvement over other packs. The bite valve on the tube doesn't leak and is easy to use. Has enough cargo space for a few extras -- I keep extra drink mix and a first aid kit in mine. The hook clip for your car keys is a nice touch.
The only minor quibble I have isn't even worth taking off a star -- it's the emergency whistle on the chest strap. The 20-mph Kansas wind is enough to make the whistle blow, which gets a little old. I put a small piece of tape on it, which solved the issue.
Used the Orange Mud pack this weekend at Dirty Kanza 200 and again, it worked flawlessly. On a day when everything else went wrong, my hydration pack was not one of them.