I've got the Aether and love it. Although it does not have the trampoline back of the Atmos, the back is mesh over a pebbly foam and it definately lets more cool air back there than the solid foam or solid fabric of some other packs. The reason I really love it however is that it is hands down the most comfortable pack I've ever had. Fits me great!
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If I wouldn't eat it at home, why would I want to eat it on the trail?