I built my own, a buddy new to the game bought a 18" barreled R15 VTR (IIRC) and had me set it up for him, mount scope sight it in etc. As a general rule I clean every new gun inside and out to remove any factory packing oils etc that may gum up the action or trigger assembly. I noticed in this process that the fire control group in the R15 seemed pretty... well for lack of a better word "chincy". It was all metal, but it was nowhere near as robust as my milspec build. I am not one of those guys that everything HAS to be milspec and all that but I trust steel barstock over tubing anyday. That said, the rifle shot great and had a better trigger pull than mine. Seem to be great rifles, and realistically you'll never probably need the beefier parts of a milspec AR unless you get the permits for full auto fire or get dumped into the sandbox. If the R15 is exactly what you want, go for it because it is a nice rifle. If you find yourself thinking you might want a couple things changed, build your own. One thing to think about if you're OCD like me is that it will be near impossible to match that camo if you want to switch stocks, grips, or forearms. If you're a tinkerer, build it. If you just want an off the shelf rifle that works, the R15 is for you.