It looks like something between the Nickelodeon Astro Crag and a piece of swiss cheese, but Timbuk2's latest sleeve has a lot of thought behind it. The casing is meant to ventilate your laptop—just watch for rain.
I've really been digging the freshly-launched sleeve. The materials feel great—soft, sturdy, and well-crafted—although I wish it gave the Air a tighter fit. Having loose room inside the sleeve makes me nervous.
But the overall rationale behind the scheme is clever, if not entirely comprehensive. Sealing up your laptop when it's still on, trapped in its own heat, is definitely a bad idea. Chips loathe heat. Then again, the Air doesn't get particularly warm when it's closed and sleeping, unlike older MacBooks. Still, if you're worried about ventilation and longevity, the porous Crater will let air in and out. Will this make a difference over the lifespan of your computer? Maybe a small one. Will it potentially let in dust and liquids? Yes. There are tradeoffs in this thing, so keep that in mind. But at the very least, the $35 Crater is more pleasing from a design standpoint than your average sleeve. [Timbuk2]