It's easier to drink more if your hands aren't cluttered up with a cigarette.

Thinking around the people I know, I don't think there's any particular tendency for the non-smokers to drink less. What makes the difference is if you're the one driving.

Irish ingenuity being what it is, if this comes into law there'll be a move away from the single bar to one where there's a separate smoking room, which won't have bar-staff working in it. And anything that breaks pubs up into rooms that way is a good thing I'd say. So long as they don't make the smoking room the session room as well.