With DD I waited a week or two I think because being my first baby I was all "my baby will NEVER have a dummy blah blah blah LOL". I was also totally paranoid it would screw up breastfeeding (it didn't). But DD never really got attached to it, she ditched it for good herself at about 7 months.

With DS I took one to the hospital and he had it from day one. He always wanted to suck on something and with a just-turned-two year old as well I couldn't sit on the couch letting him comfort suck all day long. He is still quite attached to his dummy at 15mths - I really want to get rid of it but not sure where to start now LOL.