I don't use anything except coffee, but I know some extremely talented coders who smoke (outside of work) to help with stress/anxiety/focus. It's probably something you have to evaluate for yourself, as it affects everyone differently. If it's helpful to you and improves productivity, I don't think there's anything wrong with it as long as the benefits outweigh the negatives. Maybe try tweaking how much or how frequent you smoke to see if you can reduce the side effects.

Btw, I've known founders who smoke. The only people who might care in SF are more conservative VCs etc.