I've been using one for 20 years, and would not use anything else. I've been through, RCBS, Redding, Johnson and Pacific. There are certain powders that will not meter consistant through any of these type measures, so one must either rough cut and trickle, or find a particular measure best suited for that particular powder. I have an old Belding & Mull measure that is "king of the hill" for large kernal slow powder, but is horrible for ball powder.
As was stated before, the best feature is the repeatability in the settings. I have found that some powders require a slightly different technique to dispense consistantly, but the worst offenders are still within +-.01 gr. I also like the fact that it is set up to use screw on bottles.