I just found this thread and found the last 6 or so pages I've read very useful. We've got one son who is 22 mo old now. We always thought we'd have 2-3 kids, but found parenting our DS very difficult in infancy. Like many babes, he didn't sleep well until well after his 1st bday, and needed me a lot more than my "mainstream" friends' kids seemed to. I also suffered from PPD which never got diagnosed till I lost it when he was about 9mo old.
I really feel like either he's got an inherently great personality, or we've had success sticking w/ AP methods, though. He's wonderful to be around, sleeps decent now, and dare I say, has manners? Basically I feel like every day is better than the last, and if we go back to having another kid, we're just reversing that trend. Why mess w/ it? But since it's not he way we "planned" it seems a hard thing to decide about. We don't have a bio rush (We're only 30) but the big considerations for us is to have 2 closer together in the hope that they like each other *and* to reduce the amt of time we're on one income, my retirement savings is on hold, etc... so I feel like we have to decide sooner than later.
Anyway, this thread is great... My BFF is an only and I do feel like she is much better adjusted than me socially (I was #4 of 5 kids). Her mom says that she has always been very cognizant of how precious her friends are b/c of being an only - I think we can all see the benefit in that!