Initially, Hitec recommended Karbonite servos for aircraft upto 1/4 scale. Now they aren't recommended on planes over 10lbs. I personally have seen them break gears on small model cars [X(]. I'd rather have a .01 of play in my MG gear train, than have no teeth at all in a Karbonite servo and risk loosing an entire aircraft. Obviously you've had a good run of luck, but personally I think Karbonite gears are a step backwards. In a nutshell, Hitec Karbonite geared servos are nowhere near as strong as they thought they were. Bear in mind that should a Karbonite servo fail in flight, Hitec will only replace or fix the faulty servo......like for like.

On the other hand, 5925 & 5945 servos are well worth the extra money over the karbonite alternatives, assuming one wants digital precision. Otherwise, 645 servos seem dependable and have decent performance for very little outlay. 615's in my experience are unreliable. I've seen them blow their IC's under perfectly normal conditions, without any warning. Hitec servos certainly offer more bang for your buck and I'm a big Hitec fan TBH. But having used many of their servos for various applications, I can tell you that some are more worthy than others.

Looking at the numerous horror stories here on RCU, it would seem people need to exercise caution if using these new Karbonite servos in aircraft over a few pounds.