We had always thought we would have 2 or 3 kids until after we had DD and then I knew that, "2 babies was it for me!" I have one boy and one girl, both active, intelligent kids. There isn't any question in my mind that I have no desire to have another baby (don't want to put on the weight, get up in the night for feedings, etc.). Also, another baby would further postpone the age at which DH and I would be able to retire.
I just got my tubes tied yesterday. (DH was too much of a wuss to consider vasectomy.) I'm pretty uncomfortable and taking plenty of pain pills right now, but I'm very happy that birth control is taken care of.
(DH and I have discussed that we could always adopt an older child if we feel that we're missing out later. Lots of kids out there looking for happy homes. I'm not sure that we'll ever get that "itch" to have another child, but if we do, there's always the option.)