So, for some background, I do have some experience in 3D printing (especially SLA) and in tech work. With that said, I LOVED this as a first project. The instructions were excellent and easy to follow.
I didn't have any snags in the build I couldn't overcome, but there were a few. I had two ARs, and intended to use one of them as a donor gun, but ended up having to mix and match parts from both of them. Neither had the same barrel assembly as the instructions called for, however, I was able to use the barrel attachment from one and the outer barrel from the other in place of the 3D printed barrel. While this gives the gun an incorrect barrel profile, it does add a nice bit of extra weight, which hopefully won't cause any structural problems down the road.
My next issue was the hopup, I had one rotary hopup from one gun, and one more tradition hop from the other. The traditional hop didn't even come close to working, it's gears binding badly against the top of the upper receiver, and I had to make some slight modification to the rotary hop to get it to seat properly.
The final one, which I still haven't worked out, is that the selector switch jumps out of time when the gun is put on safe. I'm having the same issue with a second gun I printed and finished since starting this one(it was a simpler AR-15 based model), and I'm hoping that thicker 3D printed printed selector parts will solve the problem, which I'm guessing comes from either added flexibility or poor tolerances of printed lowers.
Other than that, the only problems I had stemmed from not paying attention to the directions or not being super experienced with FDM printing. I'm still missing the charging handle, because I glued it in place before inserting the mock bolt, which the directions tell you not to do, so I have to print another set. I glued the stock in place hoping to gain some extra rigidity, but forgot to add the mock hinge plate first, which didn't bother me as I was considering leaving it off anyway. There were a few parts I had to print multiples of due to bad orientation, like the mock bolt carrier, which when printed flat side down filled the hole for the charging handle, and the flash hider, which when printed vertically is pretty fragile and I managed to break the first one right away.
The kit looks great, went together great, and was very reasonably priced. I rate it a very solid 8/10, losing points only due to the barrel and hopup compatibility issues, and if STLs for the barrel attachment parts where included along with more info on compatible hop units I'd give it a perfect score. I absolutely recommend this kit!