As everyone has stated, overall G&G is a solid brand. A few issues with compatibility here and there in some of their guns, however all parts can be ordered direct from G&G as their customer service in my personal experience has been good. I own a SCAR-L that I bought used and since buying a year ago I have put easily 20k BBs through it between games, plinking, and destroying things for fun. Only things that have gone on me are then trigger reset spring which is a $3 part, and finally now the wiring through the folding stock krimped and cracked and needed to be replaced. The gun has been dropped on concrete, in mud, drenched with water throughout Nightfall 1 and the only external part to give is the selector switch on the right side which simply popped off.
G&G TTs are tits out of the box. I have a team mate who owns one and he refuses to open the gun up as its been a laser since day one and he doesn't want to ruin the factory work, go figure.
Guardians of Asgaard
NO EGO, ONLY HARD WORK
Primary - Z-Custom VFC ZTW
Secondary - KWA ATP