I was in the same boat and I just got the DOS with the DDR last week. I really like that I can calibrate these pumps, then plug in that I want to dose 30 ml over 24 hours and have it make all the calculations for me.
It seems like such a small thing, but trying to figure out how many ML my old ones dosed per second, then figuring out a number of seconds I need to dispense for, then plugging that time in was a headache. Plus then a week later I would forget how many ML I was trying to dose and have to run the calculation back the other way. Not to mention the trouble when my containers would get empty,..
I'm amazed at how accurate the DOS is when compared with the old style motor, and I couldn't be happier with my choice.
Whiskey