I have been using the Deuter Race EXP Air that the OP suggested for commuting for the last 2 years (33 mile round trip, ~900' climbing each way). Absolutely great pack and not sweaty at all. Very comfortable even when heavy

BUT forget it if you are carrying shoes + clothes + lunch, its just not big enough unless you are wearing flip-flops or have toddler-sized feet. My 15" macbook pro just barely fits into it and if you are carrying a computer forget any type of footwear.

I suggest getting something 22+ litres. I use an old crappy LL bean pack about once/2 weeks to stage clothes to/from the office but it really makes me appreciate the Deuter when I wear it.