Hi,
I get on fine with my D-D regulator and wouldn't hesitate to buy another if I needed to replace it, but conversely I know of others who wouldn't touch them with a barge pole, bad experiences with the main internal seal seems to be an Achilles heal for some.
I have found the pressure gauges and the coarse adjuster to be very good but the needle valve not so great but having said that I rarely alter the needle valve anyway preferring to rely on the accuracy of the pressure gauge instead (which appears to be very consistent indeed). The solenoid valve has never let me down in two years of use (touch wood).
Regards, Chris.