I don't personally know Kevin, and am not attempting to speak for him, nor to sound like an echo. I am the (previously) unbiased owner of a Fix. Previously, because once I started shooting it, it was hard to be totally objective anymore. The Fix is simply more than the sum of its parts. If you just look at it as "AR ergos", "like an RPR", you really are missing most of it. The 45 degree bolt throw means nothing to me in and of itself. The lighter weight means nothing, in and of itself. You can fill in the rest of the features along the same lines. The point is, when you have a gun that is as light as the Fix, AND it is fully adjustable (FULLY), and the stock folds, and it takes good mags (I only shoot factory, but I do understand that you reloaders might prefer a longer COAL), and it has superior ergonomics (which allow for easier hits and less recoil), and is has a very short bolt throw, and it takes clip on NV, and it balances perfectly (more ergos), and it is capable of being configured for short and quiet, or longer and further, or anything in between, in almost any caliber that actually matters for real world use (I would love to see a long action version for my own preferences), then maybe you will start to see why the Fix is, if not revolutionary, at least extremely evolutionary. It is simply a more evolved bolt gun. Not to mention that you can do all the work at home yourself, with very little money spent on tools. Look what AI barrel change kits cost. PLus all the other stuff you need for them. The Fix requires much less, though no one will be changing barrels in the field, unless you consider a vice on your tailgate to be "the field."
Which is not to say that our older style guns are obsolete. They are still quite useful, and I like them very much. In some ways they offer advantages that the Fix currently does not. But none of them offer all the things that the Fix offers, and that is why I like it so much.
So, on to the disadvantages or possible negatives of the Fix. We will leave cost aside, because everyone on this board probably has spent a lot of money on custom or factory rifles, and value is in the eye of the owner.
As a hunting gun, which often means cold weather for me, an all metal gun like the Fix is not ideal. There are work-arounds of course, but the fact is that an all metal gun is colder in the cold and hotter in the heat. If you need or want to hand carry it, you will need to do something to mitigate the heat loss, even through warm gloves. I'm currently playing with a Triad Tactical Sniper Skid Pad on mine. The cheekpiece is plastic, so not too bad there, and easily improved if you prefer a softer or warmer option. I shoot almost everyday, regardless of weather, so I'm fairly sensitive to this stuff. Still doesn't bother me much or prevent me from loving the gun.
The full length pic rail up top is a blessing for those of us who like to clip NV in front, but it also adds a cheese grater effect, and so I will likely cover it with rubber pic rail ladders when not in use.
The AR pistol grip/trigger guard dimensions are a blessing and a curse. Awesome for working the offside safety and bolt, but not an ideal trigger reach (too short for most people) if you want to wrap around the grip. Not an issue for me, but I have smaller hands.
I know I'm leaving something out right now, but I have to run and can't remember it.
eta: The last thing that I have come up with that might stand some improvement on the Fix is the mag release button. With or without gloves, I have a hard time feeling it when I move my finger to it from ither the trigger or an index position. It is striated, and I think that large, rough cut checkering would be an improvement. I'm sure I can implement a diy fix for it, but if I could actually change one item on the gun, it would be that.