I've tried the DPM system, my curiosity got the better of me. I found that it minimized recoil some with heavier bullets (tested with Bayou Bullets 160gr and N320). It wasn't a huge difference but I would rather use it over the #10 or #11 springs. It just felt better. However with BB 135gr and N320 I liked the #10 spring better. It seemed like with the lighter bullets it would have more of a back and sling shot forward motion with DPM and the regular springs just feel nicer.
I don't use the DPM at all now, I can give you a good deal on it if you'd like