I have a Tasco PDP3 on my Ranch Rifle and am very happy with it. I traded my 1" rings for 30mm (Ruger swapped at no charge). My only regret is that Ruger doesn't make low 30mm stainless rings. I got the medium height stainless rings, and they work okay, but I would rather mount it lower. I may get some Ruger low 30mm rings in blue (though the the PDP3 and my rifle are stainless). Be careful about the later models (PDP5, etc.) - they offer nice features, but I don't think any of them will fit the standard Ruger rings.
Doug