Particularly the iPhone 4(s). It's got probably the best form factor of any phone ever made, but people put those massive black rubber things on them with a circle cut in the back to show the Apple logo. Absolute abomination.
There's various other phones that I find more visually attractive than the iPhone and a whole lot of them are more comfortable to operate (no sharp edges, lighter).
Sure, my 4S is beautiful, but it just doesn't feel right in my hand. Something about the aluminum/glass seam bothers me, and so I got a slim case and never looked back.
It's like those tiny micro-sized dogs.
It does have quite hard edges though, and I've wondered if they would get annoying after a while.
I never felt particularly either way about the 3GS hardware - it's ok, but nothing special in my opinion.
I will say that I'm the only one I know who considers the iPhone 4 to be a complete abortion of industrial design. It's fragile, it's unpleasant to hold due to sharp edges everywhere, and I almost always have to spin it around in my hands like a trained seal every time I pull it out of my pocket, because (unlike the 3GS) it's difficult to tell how it's oriented by feel alone. None of these things are true of a good design.
Apparently you can pull the SIM out of an AT&T iPhone 4 and wedge it directly into an unlocked Galaxy Nexus HSPA+, even though the iPhone takes a micro SIM. I ordered one of the latter after the iPhone 5 (non)announcement yesterday and am looking forward to seeing how that hack works.