The hardest adjustment for us was having to plan for every outting. If we suddenly wanted to go out for dinner we had to pack a whole bag, and consider our baby's schedule. Is she going to need to eat in the next hour and a half, Is this her fussy time, etc? There were no more sporadic evenings. We started having date nights in, one of us would get take out and a movie and we would eat on the couch. That way if I needed to feed the baby or if she was fussy and needed to be bounced, we could do that in the comfort of our own home.
Once the baby is old enough to leave with a babysitter it is nice to be alone again and enjoy your meal without feeling rushed. However, a simple evening out now costs twice as much because you have to pay the sitter.
Babies definately put a cramp in your social life. However, we were surprised to find that we really didn't mind that much. So even though our lives have changed dramatically we wouldn't want to go back to those pre-children days.