I've always got the impression from reading World's Finest and Superman/Batman that Clark is probably the one person Bruce trust most in the world even before Dick and Alfred. Though Bruce seems intimadated possibly even scared by Clark's utter faith in him.
I think the real symbol of their depth of their relation ship lies in the kryptonite ring Bruce possess. Clark gave Bruce the ring to stop him should he ever go rogue. Bruce has done everything in his power to avoid using it. ie. Tower of Babel, he created synthetic kryptonite to disable and not kill Clark.
An act which would have probably ruined an normal relationship, but Clark remains loyal to Bruce through everything, inculding Tower of Babel and Brother Eye. He proves his devotion time and again like in Emperor Joker when he takes on Bruce's many deaths to preserve Bruce's sanity and ensure that he is the man he supposed to be.
I've also noticed many times, how Bruce often comments on Clark's devotion to Lois, yet Lois seems to oblivious to Clark and Bruce's relationship.
The relationship between Clark and Bruce, platonic or romantic, is something unique and powerful. I guess that is why there are so many tales written about the two.