To get back to the subject at hand, Carl asked opinions on upgrading set components, here is my opinion:
It really depends.
If the components of the set are in matching condition, then I probably would not replace any pieces.
If the condition is mixed, then I see nothing wrong with upgrading pieces, so long as the correct variation is found. Of course then you are in the position of trying to match conditions.
I spent years looking for the correct variations of the cars in a mid-1960's set that I had. The locomotive was nice, but every single car, including the tender was heavily damaged.
