If set up properly, I get overcharge about 1 out of 7. That's with large extruded powder (4064, r33, n570, h1000). With easier powders (ball and smaller extruded) I almost get 100% good charges.
The key is to set it up correctly. Have it dispense slow and you have to play around with the setting for when it starts to trickle. Each powder is different.
One problem that I do have, is the accuracy. It's good for about .3gr with the large extruded. So now I use it with my gem pro 250 and hand trickle the last .2 for the larger extruded. For easier powder the accuracy is way better and I don't need to hand trickle.
I have no experience with the rcbs. But I wouldn't be surprised if the accuracy wasn't too much better with the large extruded powder.
So I guess it depends on what you need from it. If shooting groups at a 100 yards or loading ball/smaller extruded it does work and works well. If you need the lowest sd with velocity to reach out to 1000 yards or more. Then its not the best.