I've never used the Harrell measure, but I've only heard very good things about it from the guys who do use one. They claim that it's even better than the Redding competition measures. I use a Redding BR-30 competition, and a Redding 10-X competition, and both these measures are 5 times better than any RCBS, LEE, or Lyman measure I've ever used.
Like you said, once I get my micrometer's set for a given charge weight with a powder, I only have to go back to that setting to get perfect drops every time. :grin: