While in the process of turning my Dillon 550 into a single stage press, the first thing that got consigned to the junk drawer was the powder dispensing unit. (It didn't like my 2 favorite powders very much. /ubbthreads/images/graemlins/smile.gif)
I now use an RCBS Uni-Flow measure and am very happy with it.
If, by powder dispencing system you mean the electronic powder meter/thrower, all the ones I've seen seem pretty slow. JMHO.
Mike
edit - thanks for the 6mm links listed above. Very interesting info. I just checked em out.