just to provide a "simple" answer to a simple question:
NO - I do not agree with Keith's assertion as quoted.
YES - I agree with what I *believe* Keith wanted to say, which is that
"introduction of *site-scoped* addresses causes far more problems than it
solves".
I do NOT believe that introduction of link-local addresses causes far more
problems than it solves.
I see scoped addressing as a general problem, of which v6 site-locals and v4
link-locals are both examples. That said, I think v6 link-locals as "mostly
harmless" provided that we use them only for things like router discovery.
If we started expecting ordinary applications to be able to use them, I'd move
them back to the "harmful" category - they'd have most of the problems of
site-locals.