He sounds EXACTLY like my Rowdy - at 4 months he didn't bark at all - although he did go through a stage where he started barking at us to get our attention (I took care of that with proper correction). He is soooo very friendly, he loves children, loves other dogs, loves EVERYONE!
He does bark when the lab/rotty mix next door barks - he doesn't bark at whatever the lab is barking at, he is always jumping on the fence barking at the lab! Go figure.
So, take heart - Rowdy is 10 months old and he is sooooo good and well behaved and so lovey dovey!!!