Well, I have no issue with someone under 18 owning a gun if it's done with parental consent and the parent is present when the gun is used. My 8 year old son has 2 airsoft guns, a Firepower Boys M4, and a TM Boys MP5. I see nothing wrong with kids shooting as long as its done responsibly under adult supervision. Now onto the issue of the gun itself.
I have the M15A4 rifle, and it's a beautiful gun. Externally, it's about as solid as you can get. The metal is of excellent quality, as are the fibre-reinforced furniture. Now people tend to say that internal parts like the spring guide and piston assembly tend to be problematic. I've had somewhere between 15 000 and 20 000 rounds put through my STOCK gun without a hiccup.
I had mine opened up to upgrade some parts, and saw no internal wear other than very minor wear on the tappet plate where the nub on the sector gear connects with it. Otherwise, all internal parts looked like new (save for a little dirt and gear smearing from use), including the 'problematic' piston assemblies. Nonetheless, I replaced the whole compression assembly except the cylinder with Systema parts and a Prometheus spring. It's shooting a bit shy of the numbers I should be seeing, but working very well with a nice performance increase over its stock form.
I would highly recommend CA guns. This rifle has proven to me that they're reliable guns.