Yes indeed. With the MXR pedals and Boss pedals the difference was small, my MXR phase 90 gained a slight volume boost, for example. But my Zvex WM became a completely different beast, most noticably a higher output, more bass, more fuzz. My Fulltone Bass Driver grew a pair (apparantly more so with the 18v adaptor) and my Animato just seemed to sing, so much sustain.
I haven't had any popping or crackling from the Diago power supply, it's been tip top. It's expensive but I'm really happy I got one. I was always a little worried that the EffectsPowerSupplies.com supply that I was using wasn't doing my pedals any good as well. i have complete confidence in the Diago.