Ben - I'd suggest that not only is it important, it's inevitable. Whatever an architect's skills/talents in terms of routing and creating playable, interesting and strategic holes, he is still forced in some way to shape/utilize the existing site and nature itself in order to make the land suitable for the purpose; and it is in this shaping -- this transmutation of a medium into a form -- that his artistic sensibilities will emerge and be made manifest, one way or another. (The analogy I use is 'faith' -- we all have it, we all live by it, but there are many different versions of faith, i.e. some have faith that banks won't fail; some that their health is fine; some that the new car or wife will make them happy etc). I have a feeling that the architects who are most fully conscious of this fact are the ones -- for this very reason -- who do it best, i.e. who combine the art and craft most seamlessly and successfully.
Peter