To me, design or purpose is apparent.
For me, design or purpose is a figment of man's imagination.
To come to the conclusion that everything was "created by God", I think you must first have that as a preconception. It's just reading a highly human-centered view of things onto the universe.
I agree with you about all the "little details" - the inclination of the Earth is "just so", sensuality is amazing, etc. - but the conclusion I reach isn't "therefore, everything was created"; rather, my conclusion is that "if it were different, it wouldn't be the same." That's all.
If the Earth had a higher ambient radiation, or temperature, or ______, then we'd be different - and probably asking the very same questions, making the very same observations, about how things "are". It's kinda like being amazed that God created English, and how nothing would be the same without English - then you discover people speak French, and German, and...
With the intense pleasure of eating, or sex, or what-not, life would be less successful. That life is successful shows that the mechanisms in place work. We are here because of the mechanisms - it's not the mechanisms are here because we're so great.
The one thing I disagree with is the supposed superiority of man. Man is successful at modifying his environment, but I don't attach much to that beyond his ability to reproduce like rabbits (and, given the right environments, rabbits are so much more successful). Man doesn't live well at the bottom of the ocean where other species are clearly superior, in the frozen tundra, etc. This view of the superiority of man, again, is highly anthropomorphic - it's a biased view that humans must be the best based on being a human. The "supriority" needs to be defined a little.
My cat is morally superior to many humans I know. He's also superior at taking care of himself, finding food, getting along with others...