I've used both the Desmay and the Apple Bumper.
Apple Bumper Pros: Apple Bumper offers the protection discussed here, it offers the minimal protection while keeping the form factor and look of the naked phone. It's fitted perfectly, comes in a variety of colors and looks good.
Apple Bumper Cons: As much as it holds the form factor, it still adds enough size to the top, bottom, and sides to not fit in certain docks, cradles, and cases. The adapter hole on the bottom is small enough to not fit all accessories. I understand the lip creating a bezel along the front and back are there for protection when laying it down, but I was not a fan of it when typing, grabbing, if dosen't feel natural to me on this phone.
Desmay Pros: Form factor conforms to every little curve on the device. It is as close to having the phone naked with the benefit of having at least some protection, it's great scratch protection. Being that it holds the true form of the iPhone, most docks, cradles, and cases should work. The Soft touch is also a big plus, the smooth glass of the naked iPhone is slippery, the Desmay offers enough grip to feel a little more confident from accidents.
Desmay Cons: Lack of protection from drops or falls, hard to put on and take off, holes appear to not line up perfectly to the volume buttons. White logo on the lower rear center. And this is just nitpicking, but the very thin part of it in front of the adapter hole being thin tends to slightly move.
Both look great, but I settled on the Desmay. One of the reasons I love the iPhone is it's form factor, and the Desmay lets me enjoy that to the fullest, they really paid such incredible attention to detail to every fine curve, bend, and cut of the phone when they molded these.
Another option you might want to take a look at is the Snap style cases, either Incase Snap, Incipio Feather, or Casemate Barely There. Adds minimal size (Less than the Bumper) easy to install and remove, and offers a little more protection than the Desmay.