I have one with the Key Mod Lightweight Upper, grey in color. I don't remember what it is really called. I can't say that I have had any trouble with it, but it did come with the worst trigger pull I just about every seen on a AR, (like dragging a flat bottom boat across a dry creek bed), and my buddy has one also, different configuration, but has also commented that his has a terrible trigger. For a 1,400 dollar gun, it ought to have a decent trigger. But it's a moot issue now, as I did swap out the trigger and it has a nice trigger now. I guess the real test would be a lot of rounds down range, but I have heard they hold up well in that department, mine has not had that many rounds run through it, yet.
However, I think AR's are a lot like 1911's; I have never seen one yet, off of the shelf, that I didn't end up changing something on it, and sometimes quite a few things, before I was satisfied.
I think we are quite fortunate right now, in that there is a virtual sea of AR's available in many configurations at decent prices, which can allow us to find something we like, in a complete rifle, if we don't want to build from the ground up. I think in the future though, I will build one from the ground up, but I don't know if I am experienced enough to know what I really want, for sure.