Most people replying seem to be focusing on the *looks* of the new phone. Yeah, it *looks* more solid and clean and high-end as compared to the 3GS with its curved plastic back, but I definitely agree with the OP's original comments that it doesn't *feel* nearly as comfortable to hold. And I was taking some photos today and it felt so darn delicate trying to hold it in landscape mode while not covering up the camera lens in any way (and trying to describe to my brother-in-law how to hold it since he was the one who was going to take a picture of us).
I've carried my 3GS naked but I guess I need a bumper case for this, both for comfort-sake and for any possible antenna issues.
Personally, I would have preferred a more 3GS-like back, but with the matte leatherette rubbery composition for added grip.