Ammo?
In all honesty I've had one around 6 months and it has run like a champ. Bought it for ESP, 9lb recoil spring, 17lb mainspring, skateboard tape, vs grips, and a cheap Wilson Combat speed chute and Dawson magazines and it hasn't hiccup'd in 3500 rounds or so. Mainly precision or 1 hole lead 125's loaded to 1050 fps. Finally last month the extractor got loose enough to occasionally let the last round slip into the feed lips of the mag so I need to get it fixes but the gun has been perfect up till that point.
I kept spare springs on hand and that was it. Never changed one because of a problem, only when I felt it was time.