I've been using the RCBS electronic scale and infrared dispenser combination for some years now with no problems at all. However, the problems you addressed do get mentioned once in a while. As for the repeatability thing, these scales and dispensers do need to be turned on for 20 to 30 minutes before using. If they are not, they can tend to change in aprox. one tenth grain increments as you go along for a while... If you let them warm up for a while, this will not be a problem.Also, they need to be used strictly in the following conditions.
1. An absolutely solid, vibration free bench.
2. Absolutely no hint of any kind of breeze from an outside window, a furnace or air-conditioning vent or fan.
3. Away from any electronic influence such as fluorescent lights, etc.
Actually, my bench is lighted by a fluorescent fixture, but my scale/dispenser is under the door that opens up and holds my mechanical scale, and is thereby protected from the influence of those lights. I have found no sign of problems with small loads either... Dave