I bought a basic N4 a little over a year ago. In that time it has had a Daniel Defense Omega rail and a Magpul trigger guard added as well as an Aimpoint CompM3 in a Larue mount, a Blue Force Gear sling and a Surefire G2L in a Viking Tactics mount.
It has been through a class with Pat Rogers, been through a class at the Sigarms Academy, been in the hands of a variety of my cooworkers for qualifications and training, been in and out of my cruisers rack countless times, bounced around in the trunk of my car and the cab of my truck, had LOTS of 22lr fired through it with a Ciener kit . It gets cleaned from time to time and has been kept well lubed.
It’s probably had 3-4000 rounds through it since I got it. (not including .22lr)
The only real malfunctions were directly attributed to magazines. (except when I tried an extra power buffer spring AND an H2 buffer-then it choked regularly but that wasn’t the fault of the rifle!)
I know that this is nothing new but I just wanted to say how happy I am with this rifle and all of the peripheral items that have been attatched to it. It is very accurate and has never lost zero. It is as bombproof a carbine as I think you will find anywhere and I trust my life to it.
I guess they are tough to get right now but if you are in the market for a top notch carbine and can get your hands on one, buy in confidence. 
