I think my iPhone must have a fault - apparently (according to people on the internet who have no qualifications on the matter) it has a design fault that causes the aerial to drop 'bars' if you hold it the wrong way.
Mine doesn't. I think mine (and all the ones in the shop, as well as 7 of my friends who now have iPhone 4s) must have been made wrong, thus bypassing the design fault (that, if it was a design fault, should affect every iPhone 4)...
But as it doesn't, I still can't believe it's a design fault.
My 3G would get better reception if I didn't hold it (but signal is weak in my house anyway, so I'm liable to see that on any phone ever).