I came here to say the exact same thing. I used to find that the act of prying myself away from the computer to go have a cigarette was incredibly beneficial to my problem solving ability. There is definitely something to performing a simple, repetitive physical task while leaving the mind free to wander. Like the above poster, I've since quit smoking thank goodness. I don't miss the smoking itself as much as I miss having a reason to get up and treat myself to some quiet time to indulge myself in thought.

Interestingly enough browsing HN every so often is my version of this.

I don't smoke, but going out for a walk or run has that effect on me.

Nicotine also improves mental performance.