Yes it is worth it.
I had an A4000 with CD643d with scan doubler and I tested both P96 and CGX 4. It can be a bit harder to get going than P96-I recall getting black screen, but installing the latest updates fixes this.
The phase 5 hardware seems to work better with phase 5 software: better as in it feels snappier, icon dragging doesn't have re-fresh flicker, the pointer moves EXACTLY like in native screen modes, you can overclock in software and there are speed differences (although for some operations P96 is faster, but not by much).
Overall it just "feels" more right than P96 ever did for me.
