Our new place is a duplex. (Our side is the left side.) There are interesting nuances to duplex life that I don't think I was really aware of before we moved here. I would have chosen to live here anyway, as it allowed us the most square footage for our money.
For one thing, we share a wall with a complete stranger. It turns out our neighbor is pretty nice. We weren't sure at first, but so far we believe her to be very sweet. (And the entire basis for our hesitation had nothing to do with her and everything to do with a neighbor at our original house - who had lawn issues.)
So far we have discovered our neighbor to be a wheeler and dealer. She has specials for sprinkler winterization and gutter cleaning. I appreciate that actually, and it helps encourage us to do the maintenance things we sometimes let slide. (Dunno that we ever cleaned the gutters at our old house!)
The thing I appreciate most about her, is that although Peter has screamed nearly nightly for 20 minutes or more at a time (while William tries to get him to bed), she has never complained. William mentioned it one time, and she said "Yeah, sometimes I can hear him when I'm in the room next door..."
She could take the route of knocking on our door asking us to calm our wild children down so that she can think!
We do our best to keep them on the quieter side, but we also aren't going to spend all our time getting after them to be quiet. We want our kids to be allowed to be kids.
I continue to hope that over time our nice neighbor continues to be understanding. Or maybe we don't really annoy her? I can't fathom that being true, but in the mean time we will do our best to balance allowing our kids to be kids and being good neighbors.