Tony,
the PC Editor is rather old fashioned in it's format but for the type of person who is prepared to get involved to take the sounds to the next level of realism (while playing live) it is very useful and worthwhile IMO - beyond those edits that are already available/ useful onboard, in Voice Set.
But it's only for me, used for "projects" not routine use.

Note: Many voices are now switching away from "Live", "Cool" etc. types to "Super Articulation" 1 or 2 types. These latter cannot be modified in the PC Editor. Pity really.
And neither can voices that are are supplied as part of the Premium Packs.

John