Yes I do use the straps. The backpack I use (Deuter Race Exp Air Daypack) has 2 straps, 1 on the chest and the other on the waist. Very easy to lock and easy to adjust. I prefer using the straps because I find that when I am pedaling out of the saddle my old backpack (with no strap) would flop up and down and sideways. The straps keep the backpack firmly in place.

I would also highly recommend the Deuter Race Exp Air to those who want a sweat free experience (from the backpack). It is designed in such a way that the backpack itself does not rest at your back but is suspended and what touches your back is a screen/mesh that allows for free circulation of air from your back.

The Deuter Race Exp Air also accepts a water bladder if needed.