It's interesting how people have such different experiences with the same phone (well, same model I mean).
My iP4 is way, way better in terms of holding on to a useable signal than my 3G or 3GS ever were. And while I can make it drop a bar while giving it the grip-O'-death without a case, my ultra thin Incipico Feather case (which I would have bought anyway) stops all grip-induced signal attenuation. And even without a case, it hasn't yet dropped a call; my 3GS would drop calls daily. And the battery life is literally twice that as I got with the 3GS even (even when it was brand new).
Anyway, I'm quite satisfied with mine. Not at all saying people with problems don't have said problems, but just adding a story of satisfaction to the negative ones...
I've noticed that too, it's weird how some people have great experiences while others have it pretty bad. I'm kinda in the middle, it's only horrible at home, but everywhere it has been ok, as long as I have the bumper of course.