An interesting article here- link
Basically it seems that if you do moderate drinking (ie one drink a day for women, two for men) you actually gain less weight then those who don't drink at all when you look at the increase in calories as people tend to eat more fatty foods etc (ie who eats salad with a beer). It likely has something to do with how alcohol makes your metabolism kick into high gear a little bit.
Anyway kinda an interesting read. What I found interesting was how they said women consume about 350 calories a day extra on days they drink, and I find that's about right for me based on a calorie-counting app I have.