My partner has an Osprey with the air-frame (50L Exos for backpacking, so a bit of a different beast), it works, but it's not magic. I've hiked with it for a bit and it does a pretty good job of keeping sweat down, but you still sweat. It's not BS, but it still pales in comparison to the lack of sweat you get with a rack and panniers. Iff you've ruled those out, they might be your next best option.