^^^^
That's right - Some (incl me) have upgraded the front bushes to poly to better balance and deal with the stresses which occur - Well that's the theory but I'm not such an expert to be able to back it up. People who haven't upgraded the front bush haven't had any problems yet AFAIK.
Methinks it's not essential but nonetheless a good idea while fitting the WALK. Replacing any bushes on a high-miler is a good idea.