I have had a PACT Electronic Digital Power Scale and Electronic Digital Powder Dispenser for about 3 years now. While it is quite accurate it is not perfect. I generally set mine for a charge weight 1/10gr. less than I want and bump in the last 1/10gr. Mine will vary by 1/10 or so at times.
However I think you will find these types of measures are not all that speedy. Granted this depends on the granuale size of the powder (the coarser the granuales of the powder the faster it seems to dispense them) and the charge weight. Once I dump the powder charge in the case I push the dispense button on the measure. I then seat my bullet and measure the COL, and prime the next case (with my Hornady Auto Prime) in the time it takes to dispense my next powder charge.
All in all I guess I would not want to be without the one I have as it has spoiled me.
Larry