I've argued this before: Apple needs to explore new iPhone materials because the current glass back sucks. It gets dirty too easily. It's Russian-hooker naff. And it's way too fragile. Thankfully, there's a fix for that: JackBacks.
We've reviewed wooden iPhone backs before, but the JackBack feels more natural, organic and artisanal than others, most probably because the way they are finished—sealed, sanded, and finished with a Tung oil. It's very pleasant to touch. And instead of getting dirty, the more you touch it, the more beautiful it looks: Your skin oils will naturally give the wooden back an even better look and texture. After a month of use, mine looks much better than the first day.
Installation is quick and easy: Take off a pair of screws with the provided tool, take out the glass back, install this one. The iPhone 4's dimensions don't change. The JackBacks are replacements to the official glass back, with the same thickness and the same precision in the holes for the camera and flash.
And the optional laser etching—I picked a vector-based Rolling Stones tongue, but you can use any black-and-white bitmap image—is simply perfect.
The JackBack makes the iPhone get sightly warmer to the touch than the factory glass surface. Wood is an insulator, so that's natural. My iPhone has been operating normally all this time. The only real "but" is actually the price: $89 for a bamboo one without the drawing etching. The walnut model—which I think is the best texture—will push the price to $129, plus $10 for the custom etching. $139 is a lot for a back replacement, but I think the quality and the feeling is well worth that price. Your iPhone 4 will look like an entire new beast with one of these. [JackBacks]