FWIW, I've seen pics of the forthcomming NEA billet AR15 upper and the machining looked excellent - no chatter for certain.
I think the NEA AR is going to be quite nice. After speaking with them, and discussing this subject, I am confident these guys are on the right track and are sure to bring some stellar products to the table.
The flash of the camera tends to make details that aren't usually noticeable in person very apparent on photo. Do the marks stand out as much in person?
Unfortunately, the defects are visible and noticeable to the naked eye. Although I tend not to agree with the excuse, NEA is right, the majority of the machining issues are internal and likely not noticeable when the rifle is assembled. Is this something you would expect to find on a $500 dollar lower? Probably not. NEA has said they will clean things up and I respect that they are receptive to customer feed back. Good on them.
All in all, There are more positives than negatives with this lower. I can deal with a bit of machining marks, an "S" that's upside down and the dark grey colour. I'm even OK with the magazine catch solution for now. The benefits this product brings, out ways any cosmetic or otherwise flaws.
The biggest benefit of all being the use of AR mags in the Sig. For those diehards who argue for the SIG mag, try fitting three of them in a triple mag pouch. Will not work. Often in a standard double mag pouch, only one mag will fit. The other task is being able to reliable extract those mags from the pouch. Under stress and time, they tend to get a little snagged due to the mag coupling nubs on the sides. You could cut them off but, I don't know anyone who wants to cut into an OEM magazine. Of course the cheap option is the Chinese solution CANAM is selling. It all depends on what is most important to you.
The next biggest positive for me, is getting rid of that fixed length of pull stock. Now, my rifle is shorter, more easily adapted to armour and heavy clothing. I can mount a rear push button swivel! Now my one sling functions across all of my platforms. This streamlines my equipment. No need for a second sling with HK hooks on it.
Those who have trained with or use the AR platform for work, get the added benefit of some muscle memory translation over to the Swiss rifle. Admittedly, I did become quite good at magazine changes with the old Swiss mags but it always bothered me switching back and forth between two different techniques.