I think most of us that have run Dillon's for a while have come to the conclusion that most of the upgrades really don't do a whole lot. But heck, I tried them any way.
I tripped over one the other day that did improve the smoothness of the press. It replaces the index cam block with a roller bearing. My delrin indexing cam is in need of replacement. I've got a decent divit where the index cam block first contacts it.
After replacing the metal block with the bearing, the action became noticeably smoother. I suspect that it brought it back to what it used to feel like. Once I replace the delrin cam I probably won't notice any difference but here's the thing. I think that the bearing will prevent any wear what so ever on the delrin cam. Its initial touchdown area is round and is much larger than the metal block. Also, the initial movement of the bearing is instantaneous.
All in all, I think this widget actually is an improvement on my Dillon 650...