The only AF gun I own is a very early Edge. I love the gun and it is such a blast to plink and do informal target shooting. The accuracy is quite good, though I use the diopter, not a scope, so maybe some of the misses that I assume are me are actually the gun.
The first problem I had was the check valve. It was a rather poor design with a fairly short plug with a retained o-ring that slide inside the foster connector. It apparently got a little crooked and chewed up the seal enough so that it wouldn't slide back down to foster connector far enough to seal. This was in warranty and they sent me a new check valve that was simpler and could not have the same problem as the original.
Some time later I noticed that one of the maybe six bolts that holds the valve assembly to the tank was loose enough to start scratching the anodized finish off the frame. I was kind of freaked out at the prospect of getting killed by the thing, so I tightened the bolt and snugged the other ones a bit too. This was a mistake because after that it shot at an ever slower speed. I talked to AF over the phone, and at their advice I drained the tank and sent it to them. They told me that I squashed a plastic washer (or maybe a stack of plastic washers). By this time they had improved their design and had already started manufacturing them with stainless steel washers which is what they told me they used to repair my tank. I can't remember if they charged me for this or not. This was 6-7 years ago. It's been going strong ever since, though like all my guns it does not get shot as often as it used to.
I met the owner at a NRA convention about 5 years ago and he seemed like a great guy. We discussed my gun and described several incremental improvements they had made in the years since I purchased mine and offered that I could call in after the show and he would arrange to send me the associated parts. I never did put him to the test on this, but I have no reason to doubt he would have come through.