I've used one of the rcbs dispenser/scale combos for around 5 years now. Never a problem, extremely accurate and fast. When I first got it I was using a tri beam to check it all the time. I found that it was very consistent and more importantly correct every time. After I got used to using it I found that I could trust the scale just by putting the small powder cup catcher back on the scale.
After the scale is calibrated a small cup is set on the scale to catch the powder. The scale is zeroed after the empty cup is set on the scale. If the scale doesn't go back to zero every time the empty cup is put on it, there's something wrong. My rcbs hardly ever loses its zero like other models do that I've read about.
When I was looking into buy one my main concern was safety not money. I didn't want something that I'd have to check/test what it was doing every 10 throws or so. Or have to pull bullets every run to be on the safe side.
After 1000's of rounds of ammo loaded with my rcbs, I can say that I have complete confidence in it. It's a dream for doing test loads, just punch in what you want, hit the button & make up as many as you want to test.