It really depends on how much you have. It is empty calories, but if you only have one or two as a cheat meal on the weekend, than you should be OK, but if you get all sloppy every weekend, your just ruining your hard work.
another important issue with fitness and booze is the alcohol content (duh)..
alcohol does more than just give you a good time.. It lowers your GH, dehydrates you..
Some people can get away with a few pints just fine, but what I would do is track your progress that way you know if you are screwing yourself.
Here's some fun stuff-
Started tonight at about 195
Had 4 Mickeys and weighed myself-hit 202 lbs
Had 3 more and weighed myself-hit 207 lbs
I've had a few more since then and I could care less what I weigh now.