How 'bout a case that comes WITH front-back screen protection. I installed the Otterbox Defender a few days ago, and am very pleased. Screen remains responsive and clear through the built-in screen protector. Back and sides and... well, everywhere seems exceedingly well protected.
The case definitely makes the iPhone4 a lot bigger and a little heavier, but my first cell phone weighed seven pounds and had a handset on a wire... this well-protected iPhone 4 is definitely not too big for me.
The case also probably removes use of any desktop cradle - won't likely fit. But on the other hand it includes nice protective flaps over that charging connector, as well as other places on the phone that could get dirty or wet and cause trouble. I've dropped it once, and it landed with a very comforting squishy and gentle thud on a hard floor.
Only a few days so far, but so far very, very pleased.