I commuted for work for two weeks this summer in France. I had to carry a backpack style getup kind of like posted above. Not long enough like some people on here commute for years, but enough to know I was freaking miserable sweaty. I'd much rather have had panniers and something off my body.

I was keeping the power in the right zone, the only place I sweated other than my brow was a pool on my back. Yuck.

It was about 25min to work and 32ish way back, one good "hill" there and back.