If so, I'd love to hear about it. I'm quite tempted by the newer packs with ventilated back panels: the Osprey Atmos series, the Gregory Z series, the Deuter AirContact series, etc; however, I'm wondering how much the ventilation really helps keep your back cooler. Also, what are the trade-offs you've found in using a ventilated pack? And do you find the ventilation worth the trade-offs?

thanks in advance,
Derek